A. A. Menovsky

University of Amsterdam, Amsterdamo, North Holland, Netherlands

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Publications (576)1183.47 Total impact

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    ABSTRACT: Neutron diffraction is used to examine the polarization of weak static antiferromagnetism in high quality single crystalline URu2Si2. As previously documented, elastic Bragg-like diffraction develops for temperature T<T_{HO}= 17.5 K at q=(100) but not at wave vector transfer q=(001). The peak width indicates correlation lengths \xi_c=230(12) \AA \ and \xi_a=240(15) \AA. The integrated intensity of the T-dependent peaks corresponds to a sample averaged c-oriented staggered moment of \mu_{c}=0.022(1) \mu_B at T=1.7 K. The absence of T-dependent diffraction at q=(001) places a limit \mu_{\perp}<0.0011 \mu_B on an f- or d-orbital based in-plane staggered magnetic dipole moment, which is associated with multipolar orders proposed for URu_2Si_2.
    02/2014; 89(15).
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    Dataset: M2S-HTSC-6
    D. Darminto, M.O. Tjia, A.A. Menovsky
  • International Journal of Modern Physics B 01/2012; 01(02). · 0.46 Impact Factor
  • Z.koziol, J. J. M.franse, A. A.menovsky
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    ABSTRACT: A method has been developed for measuring and analysing the complex ac susceptibility of a metal undergoing a superconducting transition, in case there exists an interplay between the normal-state skin-effect and the response characteristic for the superconducting state. For the unconventional superconductor UPt3, the study of the temperature and frequency dependence of the complex conductivity close to Tc has resulted in predictions for the surface resistance and the radio-frequency susceptibility which are in a good qualitative agreement with published experimental results.
    International Journal of Modern Physics B 01/2012; 07(01n03). · 0.46 Impact Factor
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 33(3).
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    ABSTRACT: We have studied the magnetic properties of a Ho2Co15Si2 single crystal. The easy magnetization direction is parallel to the c-axis in an extended temperature region below the Curie temperature. A spin-reorientation transition takes place at 323 K, leading to an easy magnetization direction perpendicular to the c-axis below this temperature. We have compared the present results with those obtained previously on various R2Co17 single crystals and found that Si substitution not only leads to a sign reversal in the Co sublattice anisotropy but also leads to a substantial anisotropy of the saturation magnetization. Sign and magnitude of the magnetization anisotropy are conserved during the spin-reorientation transition.
    ChemInform 01/2010; 31(29).
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    ABSTRACT: Tunnelling measurements were performed on the new heavy-fermion superconductors UPd2Al3 (single crystal, Tc = 1.8 K) and UNi2Al3 (polycrystal, Tc = 1.2 K) and on the magnetic heavy-fermion superconductor URu2Si2 above and below the antiferromagnetic-ordering temperatures TN for T ≥ Tc. Tunnelling along the (a, b)-planes on UPd2Al3 shows that below TN ≈ 14 K an energy gap of about 13 meV is formed in the density of states. In contrast, no gap is found along the c-direction. For polycrystalline UNi2Al3 a gap of 10 meV is found below TN ≈ 4.8 K. Both the observed anisostropy and the values of the gaps of the new compounds prove surprisingly similar to URu2Si2. The values of the gaps appear to be set by crystal field excitation energies.
    EPL (Europhysics Letters) 07/2007; 26(3):203. · 2.26 Impact Factor
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    ABSTRACT: To investigate the nature of the superconducting transition in URu2Si2 we have made careful studies of the specific heat on oriented samples cut from a high-quality single crystal. Our high-resolution a.c.-specific-heat experiments establish the existence of only one sharp superconducting transition. Measurements in applied fields of up to 5 Tesla show that fields along both the a and c axes induce no splitting of the transition. From these Cp(H) results the upper critical field can be obtained, elucidating for the first time the bulk behaviour of Hc2(T). The large anisotropy (Hc2,a Hc2,c) and the small region of positive curvature near Tc for H||a agree with the results obtained from resistivity and a.c.-susceptibility measurements.
    EPL (Europhysics Letters) 07/2007; 19(7):637. · 2.26 Impact Factor
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    ABSTRACT: Using a high-quality single crystal of URh2Ge2 we have measured its susceptibility, magnetization, resistivity and specific heat. The materials has a highly anisotropic magnetization and resistivity, a negative-temperature coefficient of resistivity down to 35 mK, a large electronic specific-heat coefficient, and does not order magnetically. There is also no superconductivity above 35 mK. Our experiments suggest that URh2Ge2 is a unique Kondo-lattice material that neither orders magnetically nor forms a coherent ground state. A crystal-electric-field (CEF) scheme with a singlet ground state is proposed to qualitatively explain some of the results. However, for a full comparison Kondo-lattice effects and hybridization of the CEF-levels due to the strongly correlated electrons must be incorporated into a more sophisticated model.
    EPL (Europhysics Letters) 07/2007; 11(3):275. · 2.26 Impact Factor
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    ABSTRACT: The differential resistance dV/dI vs. applied voltage V for URu2Si2–normal-metal point-contacts (PCs) is investigated. For some PCs a clear double-minimum structure is observed in dV/dI vs. V at zero bias well below the superconducting critical temperature Tc as expected for the Andreev reflection. The double minimum occurs only for PCs with suppressed antiferromagnetic (AF) features in dV/dI, in support of a recent model of the gap depression by AF order in the (a,b)-plane of tetragonal URu2Si2. A strong anisotropy of the reduced gap 2Δ/kTc and of Bc2 for PCs along the a and the c axis is also observed.
    EPL (Europhysics Letters) 01/2007; 33(7):557. · 2.26 Impact Factor
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    ABSTRACT: We report x-ray absorption and magnetic circular dichroism measurements performed at the M4,5 edges of uranium in the ferromagnetic superconductor UGe2. The spectra are described with the LSDA +U electronic structure computation method. Combined with the analysis of the published (i) x-ray photoemission spectrum, (ii) electron–positron momentum density, and (iii) angular dependence of the de Haas–van Alphen frequencies, we infer for the Coulomb repulsion energy within the 5f electron shell eV. This leads to where W is the bandwidth.
    Journal of Physics Condensed Matter 03/2005; 17(15):2443. · 2.22 Impact Factor
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    ABSTRACT: The comprehensive study of charge transport in the unusual heavy fermion state of FeSi has been performed in magnetic fields H8T at T40K. The results allow to classify the anomalous and normal contributions to Hall effect and to estimate the microscopic parameters of ferromagnetic microdomains at TTC=15K. A new striking feature to be detected for the first time is an even harmonic in the angular dependencies of Hall signal in FeSi. The charge transport anomalies observed below Tm∼7K are discussed in terms of mictomagnetic ground state formation. Low-temperature magnetic H–T phase diagram of FeSi is reconstructed from the analysis of experimental data.
    Physica B Condensed Matter 01/2005; 359:1165-1167. · 1.28 Impact Factor
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    ABSTRACT: Measurements of the temperature- and field-dependent magnetic relaxation data have been conducted on a superconducting T-*-phase SmLa0.8Sr0.2CuO4-delta crystal in the vicinity of the second-peak field. The experimental data were analyzed to determine the current-dependent energy barrier, U(J), following a method proposed by Maley et al. The result was further investigated on the basis of weak collective pinning theory. It was found that the result of analysis on the temperature-dependent data was consistent with the theoretical description of thermal-disorder induced-interlayer-decoupling transition of the vortices, while its field-dependent data reveal the characteristic feature of elastic-plastic crossover of the vortex motion. (C) 2004 Elsevier B.V. All rights reserved.
    Physica C Superconductivity 10/2004; 412(1):490-496. · 0.72 Impact Factor
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    ABSTRACT: The study of galvanomagnetic, magnetic, and magnetooptical characteristics of iron monosilicide in a wide range of temperatures (1.8–40 K) and magnetic fields (up to 120 kOe) has revealed the origin of the low-temperature sign reversal of the Hall coefficient in FeSi. It is shown that this effect is associated with an increase in the amplitude of the anomalous component of the Hall resistance ρH (the amplitude increases by more than five orders of magnitude with decreasing temperature in the range 1.8–20 K). The emergence of the anomalous contribution to ρH is attributed to the transition from the spin-polaron to coherent regime of electron density fluctuations in the vicinity of Fe centers and to the formation of nanosize ferromagnetic regions, i.e., ferrons (about 10 Å in diameter), in the FeSi matrix at T<T C=15 K. An additional contribution to the Hall effect, which is observed near the temperature of sign reversal of ρH and is manifested as the second harmonic in the angular dependences ρH(ϕ), cannot be explained in the framework of traditional phenomenological models. Analysis of magnetoresistance of FeSi in the spin-polaron and coherent spin fluctuation modes shows that the sign reversal of the ratio Δρ(H)/ρ accompanied by a transition from a positive (Δρ /ρ>0, T>T m) to a negative (Δρ/ρ<0, T<T m) magnetoresistance is observed in the immediate vicinity of the mictomagnetic phase boundary at T m=7 K. The linear asymptotic form of the negative magnetoresistance Δρ/ρ ∝−H in weak magnetic fields up to 10 kOe is explained by the formation of magnetic nanoclusters from interacting ferrons in the mictomagnetic phase of FeSi at T<T m. The results are used for constructing for the first time the low-temperature magnetic phase diagram of FeSi. The effects of exchange enhancement are estimated quantitatively and the effective parameters characterizing the electron subsystem in the paramagnetic (T>T C), ferromagnetic (T m<T< T C), and mictomagnetic (T<T m) phases are determined. Analysis of anomalies in the aggregate of transport, magnetic, and magnetooptical characteristics observed in the vicinity of H m≈35 kOe at T<T m leads to the conclusion that a new collinear magnetic phase with M∥H exists on the low-temperature phase diagram of iron monosilicide.
    Journal of Experimental and Theoretical Physics 07/2004; 99(2):394-414. · 0.92 Impact Factor
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    ABSTRACT: We have performed neutron-scattering experiments on the heavy fermion superconductor URu2Si2 to search for the orbital currents predicted to exist in the ordered phase below TN=17.5K which result in a ring in momentum space. Elastic scans in the (H,K,0) and (H,0,L) planes revealed no such order parameter at low temperatures. This shows that any orbital current formation is quite small and less than our detection limit for a ring of scattering of 0.06(1)μB (albeit somewhat greater than the size of the predicted moment of ∼0.03μB). On heating, however, we find that a ring of quasielastic scattering forms in the (H,K,0) plane centered at an incommensurate radius τ=0.4 from the (1, 0, 0) antiferromagnetic (AF) Bragg position. The intensity at a point on the ring, (1.4, 0, 0), is thermally activated below TN with a characteristic energy scale of Δ=110K∼6TN. This is the coherence temperature, and it is much higher than the spin-wave energy for the selected momentum. We believe that the incommensurate spin fluctuations compete with the AF spin fluctuations, drive the transition to a disordered magnetic state above TN, and contribute to the formation of the heavy fermion state.
    Physical review. B, Condensed matter 04/2004; 69(13). · 3.77 Impact Factor
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    ABSTRACT: We report an infrared crystal field study, under magnetic field, of Nd3+ ions in non-stoichiometric La1.65Nd0.35CuO4. Two sets of crystal field excitations from the ground state multiplet 4I9/2 to the 4I11/2 and 4I13/2 excited multiplets are observed. They correspond to Nd3+ ions located in two different sites. In charge free regions, Nd3+ ion magnetic moments align parallel to the z-axis due to the Nd3+–Cu2+ magnetic interaction. Such interaction is absent in charge rich regions which leaves the corresponding Nd3+ ions in a paramagnetic state. Validity of previous calculations of CF parameters, that predict the Nd3+ electronic levels in the charge free regions as well as magnetic susceptibility anisotropy, is confirmed.
    Physica C Superconductivity 04/2004; 403(3):151-156. · 0.72 Impact Factor
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    ABSTRACT: Optical and magneto-optical properties of YVO3 single crystal were studied in the far-infrared, visible, and ultraviolet regions. Two structural phase transitions at 75 K and 200 K were observed and established to be of first and second order, respectively. The lattice has an orthorhombic Pbnm symmetry both above 200 K as well as below 75 K and is found to be either dimerized monoclinic Pb11 or triclinic P1¯ in between. We identify YVO3 as a Mott-Hubbard insulator with an optical gap of 1.6 eV. The visible spectrum shows three d-band excitations at 1.8, 2.4, and 3.3 eV, followed by charge-transfer transitions at about 4 eV. The observed structure is in good agreement with LSDA+U band structure calculations. By using ligand field considerations, we assigned these bands to the transitions to the 4A2g , 2Eg+2T1g, and 2T2g states. The strong temperature dependence of these bands is in agreement with the formation of orbital order. Despite the small net magnetic moment of 0.01 µB per vanadium, a Kerr effect of the order of 0.01° was observed for all three d bands in the magnetically ordered phase (TNéel=116 K). A surprisingly strong enhancement of the Kerr effect was found below 75 K, reaching a maximum of 0.1°. This effect is ascribed to the nonvanishing net orbital magnetic moment.
    Physical Review B 02/2004; 69:075110. · 3.66 Impact Factor
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    ABSTRACT: The tetragonal compound UNi2Si2 exhibits in zero magnetic field three different antiferromagnetic phases belowT N =124 K. They are formed by ferromagnetic basal planes, which are antiferromagnetically coupled along thec-axis with the propagation vectorq=(0, 0, q z ). Two additional order-order magnetic phase transitions are observed below T N , namely atT 1=108 K and T 2=40 K in zero magnetic field. All three phases exhibit strong uniaxial anisotropy confining the U moments to a direction parallel to the c-axis. UNi2Si2 single crystals were studied in detail by measuring bulk thermodynamic properties, such as thermal expansion, resistivity, susceptibility, and specific heat. A microscopic study using neutron diffraction was performed in magnetic fields up to 14.5 T parallel to the c-axis, and a complex magnetic phase diagram has been determined. Here, we present the analysis of specific-heat data measured in magnetic fields up to 14 T compared with the results of the neutron-diffraction study and with other thermodynamic properties of UNi2Si2.
    Central European Journal of Physics 01/2004; 2(2):397-418. · 0.91 Impact Factor
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    ABSTRACT: The optical properties of the weak magnetic metal MnSi were determined using reflectance at 80 (2–800 meV) and ellipsometry (0.8–4.5 eV). At low frequencies in the magnetic phase we observe a departure of the optical conductivity from Drude behavior: m à ðoÞ=m is strongly frequency dependent and 1=tðoÞ is approximately linear in frequency. In fact, we show that sðoÞ=sð0Þ ¼ ð1 þ io=GÞ À0:5 . Moreover, in the magnetic phase, the plasma frequency shifts to the red indicating that spectral weight is transferred to high frequencies. This is opposite to the effect recently seen in other magnetic compounds.
    Journal of Magnetism and Magnetic Materials 01/2004; 27227630(75). · 2.00 Impact Factor
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    ABSTRACT: Low field ac-susceptibility experiments have been carried out to study the effect of ``chemical'' disorder and proximity to a magnetic quantum critical point (QCP) on the non-Fermi liquid (NFL) behavior in Ce(Ru1-xRhx)2Si2 for x=0.5 and 0.6 and CeCu5.9Au0.1 . The susceptibility of strongly disordered NFL material Ce(Ru1-xRhx)2Si2 contains two components associated with different mechanisms; a disorder-driven component deltachi and a mean-field (MF) quantum critical component chiMF . deltachi exhibits H/T -scaling in the form of T-gammaf(H/T) with gamma depending on x . In contrast, the disorder-driven component has not been observed in weakly disordered NFL material CeCu5.9Au0.1 . The results of the scaling analysis strongly suggest that deltachi is due to the quantum Griffiths singularity.
    Physical Review B 01/2004; 70. · 3.66 Impact Factor

Publication Stats

6k Citations
1,183.47 Total Impact Points

Institutions

  • 1982–2014
    • University of Amsterdam
      • Van der Waals-Zeeman Institute
      Amsterdamo, North Holland, Netherlands
  • 1986–2007
    • Leiden University
      • Kamerlingh Onnes Laboratory
      Leiden, South Holland, Netherlands
  • 1995–2004
    • University of Groningen
      • Materials Science Group
      Groningen, Province of Groningen, Netherlands
    • Friedrich-Schiller-University Jena
      Jena, Thuringia, Germany
    • Dalhousie University
      Halifax, Nova Scotia, Canada
  • 2002
    • Whittier College
      Whittier, California, United States
    • European Synchrotron Radiation Facility
      Grenoble, Rhône-Alpes, France
  • 2001
    • Delft University Of Technology
      • Faculty of Applied Sciences (AS)
      Delft, South Holland, Netherlands
    • Universität Augsburg
      • Institute of Physics
      Augsberg, Bavaria, Germany
    • California State University, Los Angeles
      • Department of Physics and Astronomy
      Los Angeles, CA, United States
  • 2000
    • Sapienza University of Rome
      Roma, Latium, Italy
  • 1999
    • Tata Institute of Fundamental Research
      • Department of Condensed Matter Physics and Materials Science
      Mumbai, Mahārāshtra, India
    • Institut Laue-Langevin
      Grenoble, Rhône-Alpes, France
  • 1998
    • University of Toronto
      • Department of Physics
      Toronto, Ontario, Canada
  • 1996
    • Pedagogical University of Cracow
      • Institute of Physics
      Cracovia, Lesser Poland Voivodeship, Poland
  • 1994
    • Slovak Academy of Sciences
      • Institute of Experimental Physics
      Bratislava, Bratislavsky Kraj, Slovakia
    • American Physical Society
      Maryland, United States
  • 1992
    • B.Verkin Institute for Low Temperature Physics and Engineering
      Charkow, Kharkivs’ka Oblast’, Ukraine
  • 1988
    • French National Centre for Scientific Research
      • Institut Néel
      Lutetia Parisorum, Île-de-France, France