V. O. Garlea

Oak Ridge National Laboratory, Oak Ridge, Florida, United States

Are you V. O. Garlea?

Claim your profile

Publications (106)303.79 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The ferrimagnetic spinel $CoV_2O_4$ has been a topic of intense recent interest, both as a frustrated insulator with unquenched orbital degeneracy and as a near-itinerant magnet which can be driven metallic with moderate applied pressure. Central outstanding questions include the number and form of magnetic transitions in this material, and the absence of any degeneracy breaking structural phase transition, contrary to all available models. To help address these questions, we have performed a series of neutron diffraction and inelastic scattering measurements on $CoV_2O_4$ powders with minimal cation site disorder. Our data indicate a near ideal cubic spinel structure at all temperatures, and a ferrimagnetic spin state below $T_N = 156 K$, consistent with previous reports. Significantly however, we also provide strong evidence for a weak ($\frac{\Delta a}{a} \sim 10^{-4}$), first order structural phase transition at $T^*$ = 90 K, the same temperature where spin canting is seen in recent single crystal measurements. This transition is characterized by a short-range distortion of oxygen octahedral positions, and a weak $\Delta\sim 1.25 meV$ spin gap is observed in low temperature inelastic data. Together, these findings provide strong support for the local orbital picture and the existence of an orbital glass state below $T^*$. We further rule out in our sample the presence of additional structural or magnetic transitions at lower temperatures, contrary to other studies.
  • [Show abstract] [Hide abstract]
    ABSTRACT: A new series of transition metal vanadates, namely, Ba2M(VO4)2(OH) (M = V(3+), Mn(3+), and Fe(3+)), was synthesized as large single crystals hydrothermally in 5 M NaOH solution at 580 °C and 1 kbar. This new series of compounds is structurally reminiscent of the brackebuschite mineral type. The structure of Ba2V(VO4)2(OH) is monoclinic in space group P21/m, a = 7.8783(2) Å, b = 6.1369(1) Å, c = 9.1836(2) Å, β = 113.07(3)°, V = 408.51(2) Å(3). The other structures are similar and consist of one-dimensional trans edge-shared distorted octahedral chains running along the b-axis. The vanadate groups bridge across edges of their tetrahedra. Structural analysis of the Ba2Mn(VO4)2(OH) analogue yielded a new understanding of the Jahn-Teller effect in this structure type. Raman and infrared spectra were investigated to observe the fundamental vanadate and hydroxide vibrational modes. Single-crystal temperature-dependent magnetic studies on Ba2V(VO4)2(OH) reveal a broad feature over a wide temperature range with maximum at ∼100 K indicating that an energy gap could exist between the antiferromagnetic singlet ground state and excited triplet states, making it potentially of interest for quantum magnetism studies.
    Inorganic Chemistry 07/2015; 54(14). DOI:10.1021/acs.inorgchem.5b01037 · 4.79 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We have investigated polycrystalline samples of the zigzag chain system BaTb$_2$O$_4$ with a combination of magnetic susceptibility, heat capacity, neutron powder diffraction, and muon spin relaxation measurements. Despite the onset of Tb$^{3+}$ short-range antiferromagnetic correlations at $|\theta_{CW}|$ $=$ 18.5 K and a very large effective moment, our combined measurements indicate that BaTb$_2$O$_4$ remains paramagnetic down to 0.095 K. The magnetic properties of this material show striking similarities to the pyrochlore antiferromagnet Tb$_2$Ti$_2$O$_7$, and therefore we propose that BaTb$_2$O$_4$ is a new large moment spin liquid candidate.
  • [Show abstract] [Hide abstract]
    ABSTRACT: We describe why Ising spin chains with competing interactions in ${\mathrm{SrHo}}_{2}{\mathrm{O}}_{4}$ segregate into ordered and disordered ensembles at low temperatures $(T)$. Using elastic neutron scattering, magnetization, and specific heat measurements, the two distinct spin chains are inferred to have N\'eel $($\uparrow${}$\downarrow${}$\uparrow${}$\downarrow${})$ and double-N\'eel $($\uparrow${}$\uparrow${}$\downarrow${}$\downarrow${})$ ground states, respectively. Below ${T}_{\mathrm{N}}=0.68(2)\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, the N\'eel chains develop three-dimensional long range order (LRO), which arrests further thermal equilibration of the double-N\'eel chains so they remain in a disordered incommensurate state for $T$ below ${T}_{\mathrm{S}}=0.52(2)\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. ${\mathrm{SrHo}}_{2}{\mathrm{O}}_{4}$ distills an important feature of incommensurate low dimensional magnetism: kinetically trapped topological defects in a $\text{quasi}$-${}d$-${}\text{dimensional}$ spin system can preclude order in $d+1$ dimensions.
    Physical Review B 02/2015; 91(5). DOI:10.1103/PhysRevB.91.054424 · 3.74 Impact Factor
  • Source
    The European Physical Journal Conferences 01/2015; 83:03017. DOI:10.1051/epjconf/20158303017
  • M. R. Koehler · V. O. Garlea · M.A. McGuire · L. Jia · V. Keppens
    [Show abstract] [Hide abstract]
    ABSTRACT: Tb6FeBi2 adopts a noncentrosymmetric crystal structure and orders ferromagnetically at T-C1 = 250 K with an additional magnetic transition at T-C2 = 60 K. The low temperature magnetoelastic response in this material is strong, and is enhanced by cobalt substitution. Here, the temperature dependence of the atomic and magnetic structure of Tb6Fe1-xCoxBi2 (x = 0, 0.125, 0.25, and 0.375) is reported from powder X-ray diffraction (XRD) and powder neutron diffraction (PND) measurements. Below the Neel temperature a ferrimagnetic ordering between the terbium and iron moments exists in all compounds studied. Related to the enhanced magnetostructural response, the Co-doped compounds undergo a crystallographic phase transition below about 60 K. This transition also involves a canting of the magnetic moments away from the c-axis. The structural transition is sluggish and not fully completed in the parent Tb6FeBi2 compound, where a mixture of monoclinic and hexagonal phases is identified below 60 K. The spin reorientation transition is discussed in terms of competing exchange interactions and magnetocrystalline anisotropies of the two Tb sites and Fe/Co sublattices.
    Journal of Alloys and Compounds 12/2014; 615:514-520. DOI:10.1016/j.jallcom.2014.06.183 · 2.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The $A{R}_{2}{\text{O}}_{4}$ family ($R=\text{rare}$ earth) has recently been attracting interest as a new series of frustrated magnets, with the magnetic $R$ atoms forming zigzag chains running along the $c$ axis. We have investigated polycrystalline ${\mathrm{BaNd}}_{2}{\mathrm{O}}_{4}$ with a combination of magnetization, heat-capacity, and neutron powder diffraction measurements. Magnetic Bragg peaks are observed below ${T}_{N}=1.7\phantom{\rule{4pt}{0ex}}\mathrm{K}$, and they can be indexed with a propagation vector of $\stackrel{P\vec}{k}=(0,1/2,1/2)$. The signal from magnetic diffraction is well described by long-range ordering of only one of the two types of Nd zigzag chains, with collinear up-up-down-down intrachain spin configurations (double N\'eel state). Furthermore, low-temperature magnetization and heat-capacity measurements reveal two magnetic-field-induced spin transitions at 2.75 and 4 T for $T=0.46\phantom{\rule{4pt}{0ex}}\mathrm{K}$. The high-field phase is paramagnetic, while the intermediate-field state may arise from a spin transition of the long-range ordered Nd chains. One possible candidate for the field-induced ordered state corresponds to an up-up-down intrachain spin configuration, as predicted for a classical ${J}_{1}$-${}{J}_{2}$ Ising chain with a double N\'eel ground state in zero field.
    Physical Review B 10/2014; 90(13). DOI:10.1103/PhysRevB.90.134403 · 3.74 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present a study of the crystal structure and physical properties of single crystals of a new Fe-based ternary compound, Zr2−xFe4Si16−y(x = 0.81, y = 6.06). Zr1.19Fe4Si9.94 is a layered compound, where stoichiometric β-FeSi2-derived slabs are separated by Zr-Si planes with substantial numbers of vacancies. High resolution transmission electron microscopy (HRTEM) experiments show that these Zr-Si layers consist of 3.5 nm domains where the Zr and Si vacancies are ordered within a supercell sixteen times the volume of the stoichiometric cell. Within these domains, the occupancies of the Zr and Si sites obey symmetry rules that permit only certain compositions, none of which by themselves reproduce the average composition found in x-ray diffraction experiments. Magnetic susceptibility and magnetization measurements reveal a small but appreciable number of magnetic moments that remain freely fluctuating to 1.8 K, while neutron diffraction confirms the absence of bulk magnetic order with a moment of 0.2μB or larger down to 1.5 K. Electrical resistivity measurements find that Zr1.19Fe4Si9.94 is metallic, and the modest value of the Sommerfeld coefficient of the specific heat γ = C/T suggests that quasi-particle masses are not particularly strongly enhanced. The onset of superconductivity at Tc 6 K results in a partial resistive transition and a small Meissner signal, although a bulk-like transition is found in the specific heat. Sharp peaks in the ac susceptibility signal the interplay of the normal skin depth and the London penetration depth, typical of a system in which nano-sized superconducting grains are separated by a non-superconducting host. Ultra low field differential magnetic susceptibility measurements reveal the presence of a surprisingly large number of trace magnetic and superconducting phases, suggesting that the Zr-Fe-Si ternary system could be a potentially rich source of new bulk superconductors.
    Journal of Physics Condensed Matter 08/2014; 26(37):376002. DOI:10.1088/0953-8984/26/37/376002 · 2.35 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Quaternary phases La1–xNdxCo2P2 (x = 0, 0.12, 0.25, 0.37, 0.50, 0.63, 0.75, 0.88, 1.0) have been synthesized from Sn flux to investigate the origins of drastic differences in properties between ferromagnetic LaCo2P2 and antiferromagnetic NdCo2P2. Powder and single-crystal X-ray diffraction indicate that all La1–xNdxCo2P2 samples are isostructural and crystallize in the ThCr2Si2 structure type. The unit cell parameters and volume change non-linearly with the Nd content (x), with the x < 0.50 samples being closer to LaCo2P2 and the ones with x > 0.50 being closer to NdCo2P2. These structural differences are also reflected in the magnetic behavior. The samples with lower Nd content are characterized by ferromagnetic ordering in the Co sublattice with the TC increasing from 132 K for x = 0 to 262 K for x = 0.50, while the samples with higher Nd content exhibit suppressed magnetization in the Co sublattice and canted antiferromagnetic ordering with TC ~ 270 K. Refinement of neutron powder diffraction patterns for x = 0.50 and 0.75 reveals a gradual ordering of the Nd 4f moments under the influence of Co 3d moments below 100 K. At low temperatures and zero field, these samples exhibit antiferromagnetic ordering of both Nd and Co magnetic moments, but under applied field they demonstrate the stabilization of a ferrimagnetic state with antiparallel alignment of the 4f and 3d moments, as indicated by isothermal magnetization measurements. The re-entrant ferrimagnetic transition is also observed in samples with x > 0.50 if the temperature is lowered below 5 K. The occurrence of this low-temperature magnetic transition was confirmed by alternating-current susceptibility measurements.
    07/2014; 2(36). DOI:10.1039/C4TC00564C
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The AR$_2$O$_4$ family (R = rare earth) have recently been attracting interest as a new series of frustrated magnets, with the magnetic R atoms forming zigzag chains running along the $c$-axis. We have investigated polycrystalline BaNd$_2$O$_4$ with a combination of magnetization, heat capacity, and neutron powder diffraction (NPD) measurements. Magnetic Bragg peaks are observed below $T_N$ $=$ 1.7 K, and they can be indexed with a propagation vector of $\vec{k}$ $=$ (0 1/2 1/2). The signal from magnetic diffraction is well described by long-range ordering from only one of the two types of Nd zigzag chains, with collinear up-up-down-down intrachain spin configurations. Furthermore, low temperature magnetization and heat capacity measurements reveal two field-induced spin transitions at 2.5 T and 4 T for $T$ $=$ 0.46 K. The high field phase is paramagnetic, while the intermediate field state may arise from a spin transition of the long-range ordered Nd chains, resulting in an up-up-down intrachain spin configuration. The proposed intermediate field state is consistent with the magnetic structure determined in zero field for these chains by NPD, as both phases are predicted for the classical Ising chain model with nearest neighbor and next nearest neighbor interactions.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The effects of lithium absorption on the crystal structure and electronic properties of IrSi3, a binary silicide with a noncentrosymmetric crystal structure, were studied. X-ray and neutron diffraction experiments revealed that hexagonal IrSi3 (space group P6_3mc) transforms into trigonal Li2IrSi3 (space group P31c) upon lithium absorption. The structure of Li2IrSi3 is found to consist of a planar Kagome network of silicon atoms with Li and Ir spaced at unequal distances between the Kagome layers, resulting in a polar structure along the c-axis. Li2IrSi3 exhibited type-II superconductivity with a transition temperature of Tc = 3.8 K, displaying a structure type that no previous superconductors have been reported to have.
    Journal of the Physical Society of Japan 07/2014; 83(9). DOI:10.7566/JPSJ.83.093706 · 1.48 Impact Factor
  • Source
    Michael A. McGuire · V. Ovidiu Garlea · Andrew F. May · Brian C. Sales
    [Show abstract] [Hide abstract]
    ABSTRACT: Analysis of neutron diffraction, dc magnetization, ac magnetic susceptibility, heat capacity, and electrical resistivity for DyRuAsO in an applied magnetic field are presented at temperatures near and below those at which the structural distortion (T_S = 25 K) and subsequent magnetic ordering (T_N = 10.5 K) take place. Powder neutron diffraction is used to determine the antiferromagnetic order of Dy moments of magnitude 7.6(1) mu_B in the absence of a magnetic field, and demonstrate the reorientation of the moments into a ferromagnetic configuration upon application of a magnetic field. Dy magnetism is identified as the driving force for the structural distortion. The magnetic structure of analogous TbRuAsO is also reported. Competition between the two magnetically ordered states in DyRuAsO is found to produce unusual physical properties in applied magnetic fields at low temperature. An additional phase transition near T* = 3 K is observed in heat capacity and other properties in fields greater than about 3 T. Magnetic fields of this magnitude also induce spin-glass-like behavior including thermal and magnetic hysteresis, divergence of zero-field-cooled and field-cooled magnetization, frequency dependent anomalies in ac magnetic susceptibility, and slow relaxation of the magnetization. This is remarkable since DyRuAsO is a stoichiometric material with no disorder detected by neutron diffraction, and suggests analogies with spin-ice compounds and related materials with strong geometric frustration.
    Physical Review B 07/2014; 90(1). DOI:10.1103/PhysRevB.90.014425 · 3.74 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We describe why Ising spin chains with competing interactions in $\rm SrHo_2O_4$ segregate into ordered and disordered ensembles at low $T$. Using elastic neutron scattering, magnetization, and specific heat measurements, the two distinct spin chains are inferred to have N\'eel ($\uparrow\downarrow\uparrow\downarrow$) and double-N\'eel ($\uparrow\uparrow\downarrow\downarrow$) ground states respectively. Below $T_\mathrm{N}=0.68(2)$ K, the N\'eel chains develop three dimensional (3D) long range order (LRO), which causes the double-N\'eel chains to freeze into a disordered incommensurate state at $T_\mathrm{S}= 0.52(2)$ K. $\rm SrHo_2O_4$ distills an important feature of incommensurate low dimensional magnetism: kinetically trapped topological defects in a quasi$-d-$dimensional spin system can preclude order in $d+1$ dimensions.
  • Source
    Z L Dun · V O Garlea · C Yu · Y Ren · E S Choi · H M Zhang · S Dong · H D Zhou
    [Show abstract] [Hide abstract]
    ABSTRACT: A layered perovskite LaSrVO 4 was studied by neutron diffraction, pair distribution function measurement using synchrotron x-ray, susceptibility, and specific heat measurements, and first-principles calculation. The results show (i) a weak structural distortion around 100 K with the existence of orbital fluctuations both above and below it; (ii) the absence of the long range magnetic ordering down to 0.35 K but the appearance of a short range magnetic ordering around 11 K with a T 2 behavior of the specific heat below it. Meanwhile, the calculation based on the density functional theory predicts a magnetic ordered ground state. All facts indicate a melting of the magnetic ordering due to the orbital fluctuations in LaSrVO 4 , which makes it a rare candidate for the spin-orbital liquid state related to t 2g orbitals.
    Physical Review B 06/2014; 89(23). DOI:10.1103/PhysRevB.89.235131 · 3.74 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Four rare-earth cobalt arsenides, RCo2As2 (R = La, Ce, Pr, Nd), were obtained by reactions of constituent elements in molten Bi. The use of Bi flux also allowed the growth of representative single crystals. All compounds are isostructural and belong to the ThCr2Si2 type (space group I4/mmm). The formation of Co vacancies is observed in all structures, while the structures of La- and Ce-containing compounds also show incorporation of minor Bi defects next to the R crystallographic site. Correspondingly, the general formula of these materials can be written as R1–xBixCo2−δAs2, with x/δ = 0.03/0.1, 0.05/0.15, 0/0.2, and 0/0.3 for R = La, Ce, Pr, and Nd, respectively. All compounds exhibit high-temperature ferromagnetic ordering of Co magnetic moments in the range 60–200 K. Electronic band structure calculations revealed a high peak in the density of states at the Fermi level, thus supporting the itinerant nature of magnetism in the Co sublattice. The magnetic ordering in the lanthanide sublattice takes place at lower temperatures, with the R moments aligning antiparallel to the Co moments to give a ferrimagnetic ground state. The measurements on oriented single crystals demonstrated significant magnetic anisotropy in the ferrimagnetic state, with the preferred moment alignment along the c axis of the tetragonal lattice. Neutron powder diffraction failed to reveal the structure of magnetically ordered states but confirmed the presence of Co vacancies. X-ray absorption near-edge structure spectroscopy on Ce1.95Bi0.05Co1.85As2 showed the average oxidation state of Ce to be +3.06. Solid state NMR spectroscopy revealed a substantially reduced hyperfine field on the Co atoms in the vicinity of Bi defects.
    Chemistry of Materials 05/2014; 26(12):3825-3837. DOI:10.1021/cm501522v · 8.54 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Fe_{1+y}Te with y≲0.05 exhibits a first-order phase transition on cooling to a state with a lowered structural symmetry, bicollinear antiferromagnetic order, and metallic conductivity, dρ/dT>0. Here, we study samples with y=0.09(1), where the frustration effects of the interstitial Fe decouple different orders, leading to a sequence of transitions. While the lattice distortion is closely followed by incommensurate magnetic order, the development of bicollinear order and metallic electronic coherence is uniquely associated with a separate hysteretic first-order transition, at a markedly lower temperature, to a phase with dramatically enhanced bond-order wave (BOW) order. The BOW state suggests ferro-orbital ordering, where electronic delocalization in ferromagnetic zigzag chains decreases local spin and results in metallic transport.
    Physical Review Letters 05/2014; 112(18):187202. · 7.51 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Neutron and X-ray diffraction, magnetic susceptibility, and specific heat measurements have been used to investigate the magnetic and structural phase transitions of the spinel system Fe1+xCr2-xO4(0.0<=x<=1.0). The temperature versus Fe concentration (x) phase diagram features two magnetically ordered states and four structural states below 420 K. The complexity of the phase diagram is closely related to the change in the spin and orbital degrees of freedom induced by substitution of Fe ions for Cr ions. The systematic change in the crystal structure is explained by the combined effects of Jahn-Teller distortion, spin-lattice interaction, Fe2+-Fe3+ hopping, and disorder among Fe2+, Fe3+, and Cr3+ ions.
    Physical Review B 04/2014; 89(13). DOI:10.1103/PhysRevB.89.134106 · 3.74 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The spinel vanadates have become a model family for exploring orbital order on the frustrated pyrochlore lattice, and recent debate has focused on the symmetry of local crystal fields at the cation sites. Here, we present neutron scattering measurements of the magnetic excitation spectrum in $\mathrm{FeV_2O_4}$, a recent example of a ferrimagnetic spinel vanadate which is available in single crystal form. We report the existence of two emergent magnon modes at low temperatures, which draw strong parallels with the closely related material, $\mathrm{MnV_2O_4}$. We were able to reproduce the essential elements of both the magnetic ordering pattern and the dispersion of the inelastic modes with semi- classical spin wave calculations, using a minimal model that implies a sizeable single-ion anisotropy on the vanadium sublattice. Taking into account the direction of ordered spins, we associate this anisotropy with the large trigonal distortion of $\mathrm{VO_6}$ octahedra, previously observed via neutron powder diffraction measurements. We further report on the spin gap, which is an order-of-magnitude larger than that observed in $\mathrm{MnV_2O_4}$. By looking at the overall temperature dependence, we were able to show that the gap magnitude is largely associated with the ferro-orbital order known to exist on the iron sublattice, but the contribution to the gap from the vanadium sublattice is in fact comparable to what is reported in the Mn compound. This reinforces the conclusion that the spin canting transition is associated with the ordering of vanadium orbitals in this system, and closer analysis indicates closely related physics underlying orbital transitions in $\mathrm{FeV_2O_4}$ and $\mathrm{MnV_2O_4}$.
    Physical Review B 03/2014; 89(22). DOI:10.1103/PhysRevB.89.224404 · 3.74 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The novel iron-based compound, BaYFeO4, crystallizes in the Pnma space group with two distinct Fe(3+) sites, that are alternately corner-shared [FeO5](7-) square pyramids and [FeO6](9-) octahedra, forming into [Fe4O18](24-) rings, which propagate as columns along the b-axis. A recent report shows two discernible antiferromagnetic (AFM) transitions at 36 and 48 K in the susceptibility, yet heat capacity measurements reveal no magnetic phase transitions at these temperatures. An upturn in the magnetic susceptibility measurements up to 400 K suggests the presence of short-range magnetic behavior at higher temperatures. In this Article, variable-temperature neutron powder diffraction and high-temperature magnetic susceptibility measurements were performed to clarify the magnetic behavior. Neutron powder diffraction confirmed that the two magnetic transitions observed at 36 and 48 K are due to long-range magnetic order. Below 48 K, the magnetic structure was determined as a spin-density wave (SDW) with a propagation vector, k = (0, 0, (1)/3), and the moments along the b-axis, whereas the structure becomes an incommensurate cycloid [k = (0, 0, ∼0.35)] below 36 K with the moments within the bc-plane. However, for both cases the ordered moments on Fe(3+) are only of the order ∼3.0 μB, smaller than the expected values near 4.5 μB, indicating that significant components of the Fe moments remain paramagnetic to the lowest temperature studied, 6 K. Moreover, new high-temperature magnetic susceptibility measurements revealed a peak maximum at ∼550 K indicative of short-range spin correlations. It is postulated that most of the magnetic entropy is thus removed at high temperatures which could explain the absence of heat capacity anomalies at the long-range ordering temperatures. Published spin dimer calculations, which appear to suggest a k = (0, 0, 0) magnetic structure, and allow for neither low dimensionality nor geometric frustration, are inadequate to explain the observed complex magnetic structure.
    Inorganic Chemistry 01/2014; 53(2). DOI:10.1021/ic4026798 · 4.79 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Results of magnetic field and temperature dependent neutron diffraction and magnetization measurements on oxy-arsenate Rb$_{2}$Fe$_{2}$O(AsO$_{4}$)$_{2}$ are reported. The crystal structure of this compound contains pseudo-one-dimensional [Fe$_{2}$O$_{6}$]$^\infty$ sawtooth-like chains, formed by corner sharing isosceles triangles of $Fe^{3+}$ ions occupying two nonequivalent crystallographic sites. The chains extend infinitely along the crystallographic $b$-axis and are structurally confined from one another via diamagnetic (AsO$_{4}$)$^{3-}$ units along the $a$-axis, and Rb$^+$ cations along the $c$-axis direction. Neutron diffraction measurements indicate the onset of a long range antiferromagnetic order below approximately 25 K. The magnetic structure consists of ferrimagnetic chains which are antiferromagnetically coupled with each other. Within each chain, one of the two Fe sites carries a moment which lies along the \emph{b}-axis, while the second site bears a canted moment in the opposite direction. Externally applied magnetic field induces a transition to a ferrimagnetic state, in which the coupling between the sawtooth chains becomes ferromagnetic. Magnetization measurements performed on optically-aligned single crystals reveal evidence for an uncompensated magnetization at low magnetic fields that could emerge from to a phase-segregated state with ferrimagnetic inclusions or from antiferromagnetic domain walls. The observed magnetic states and the competition between them is expected to arise from strongly frustrated interactions within the sawtooth chains and relatively weak coupling between them.

Publication Stats

520 Citations
303.79 Total Impact Points

Institutions

  • 2007–2015
    • Oak Ridge National Laboratory
      • • Quantum Condensed Matter Division
      • • Neutron Scattering Science Division
      Oak Ridge, Florida, United States
  • 2010–2014
    • McMaster University
      • Department of Chemistry and Chemical Biology
      Hamilton, Ontario, Canada
  • 2013
    • Princeton University
      • Department of Chemistry
      Princeton, New Jersey, United States
  • 2006–2013
    • University Joseph Fourier - Grenoble 1
      • Institut Néel
      Grenoble, Rhône-Alpes, France
  • 2012
    • Los Alamos National Laboratory
      • Lujan Neutron Scattering Center
      Лос-Аламос, California, United States
  • 2005–2009
    • Iowa State University
      • • Ames Laboratory
      • • Department of Physics and Astronomy
      Ames, IA, United States