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ABSTRACT: Ferrimagnetic Mn2As thin films with perpendicular magnetic anisotropy were successfully grown on Si(100) by molecular-beam epitaxy. From the reflection high-energy electron diffraction and X-ray diffraction patterns, the orientation of the Mn2As film on Si was along the c-axis in the tetragonal crystal structure. Mn2As film exhibited ferrimagnetic ordering at temperatures greater than 300 K, which differs from antiferromagnetic or paramagnetic behaviors in the bulk form. The magnetic moment of Mn2As determined by saturated magnetization was 0.51 µB per unit cell.
Journal of Applied Physics 03/2011; 109(6):063914-063914-4. · 2.17 Impact Factor
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ABSTRACT: We report here a systematic study of Cr–Mn alloy films that have been epitaxially stabilized on GaSb (100) using molecular beam epitaxy. The crystal structural transition between the α-Cr-type and the α-Mn-type for the Cr–Mn alloy films is observed along with changes in growth temperature, film thickness, and the ratio of Cr to Mn. Ferrimagnetism is observed in the Cr–Mn films containing the α-Mn-type phase based on the magnetic field-dependent anomalous Hall effect hysteresis and is corroborated by the magnetization hysteresis. The α-Mn-type CrMn phase at the expanded lattice parameter induces the observed ferrimagnetic ordering. The magnetic moments of Cr–Mn films can be tuned by adjusting the growth temperature, film thickness, and the ratio of Cr to Mn. Eventually, new structural and magnetic phase diagrams of the epitaxial Cr–Mn alloy films are established. The results of this study can prove helpful in both forming a comprehensive understanding of Cr–Mn alloys and in finding new applications for it in spintronic devices.
Journal of Applied Physics 10/2010; 108(7):073915-073915-6. · 2.17 Impact Factor
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ABSTRACT: We report on the epitaxial stabilization and magnetic properties of Mn films on GaSb(100) using molecular beam epitaxy, a follow-up to our previous work on the growth of Mn films on GaAs(100) [Phys. Rev. B 79, 045309 (2009)]. A strong ferrimagnetic ordering was observed which was attributed to the largely expanded lattice parameter resulting from the lattice mismatch with substrate and the enhanced thermal energy with increasing growth temperature. The observed magnetic moment of 1.16μ<sub> B </sub>/ Mn atom was several times larger than that observed in the Mn/GaAs(100) films due to the lattice constant difference of substrates. The in-plane magnetoresistance behavior demonstrated the magnetic anisotropy that might result from the slightly distorted cubic structure of α -Mn phase under low-dimensional growth.
Journal of Applied Physics 06/2010; · 2.17 Impact Factor
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ABSTRACT: For two-terminal devices fabricated by Be (or Mn)-doped p-type epitaxial GaAs thin films, when the Mott metal-insulator transition (MIT) as current jump occurs, we observe that the energy gap of GaAs is not shifted, its peak intensity decreases in an applied voltage, and that the MIT temperature is between 410 and 440 K, and that the current jump is controlled by temperature, voltage and light intensity. The control of the jump voltage, a characteristic of the Mott MIT, reveals that these devices can be applied for programmable critical temperature sensors or optical sensors with high sensitivity.
Applied Physics Letters 12/2009; 95(23):231910-231910-3. · 3.84 Impact Factor
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ABSTRACT: We have successfully fabricated an epitaxial Mn-doped p-type GaAs thin film on a GaAs(001) substrate by using molecular beam epitaxy at a substrate temperature of 500 • C. For the Mn-doped GaAs thin film with a hole concentration of np ≈ 2.0 × 10 17 cm −3 , an abrupt first-order metal-insulator transition (MIT) is observed at room temperature. The temperature dependence of the resistivity does not show a structural phase transition up to 420 K. The MIT temperature is controlled by applying a voltage without external hole doping. The abrupt MIT is discussed, along with breakdown.
Journal- Korean Physical Society 04/2007; 50. · 0.45 Impact Factor
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ABSTRACT: We gave grown (Fe<sub>x</sub>Mn<sub>1-x</sub>)<sub>2</sub>As thin films on n-type Si (001) substrate using molecular beam epitaxy (MBE) at the substrate temperature, Ts=300degC. We found that the crystal structure of (Fe<sub>x</sub>Mn<sub>1-x</sub>)<sub>2</sub>As thin films was the tetragonal Mn<sub>2</sub>As type. From the magnetization measurement of (Fe<sub>0.67</sub>Mn<sub>0.33</sub>)<sub>2</sub>As thin film shows the ferrimagnetic ordering at above room temperature.
Nanotechnology Materials and Devices Conference, 2006. NMDC 2006. IEEE; 11/2006
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Jiyoun Choi, Jeongyong Choi,
Sungyoul Choi,
Soon Cheol Hong,
Sunglae Cho,
M H Sohn,
Yongsup Park,
Kyu-Won Lee,
Hyun-Min Park,
Jong Hyun Song,
J B Ketterson
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ABSTRACT: We have grown a 37-period GaSb(2 A)/MnSb(A) superlattice on GaAs(001) substrate with 100 A GaSb buffer layer by solid-source molecular beam epitaxy. We have observed that the streaky RHEED patterns of GaSb and MnSb were maintained even when the growth was finished in 37 periods, indicating 2-dimensional layer-by-layer growth of MnSb on GaSb or vice versa. In-terestingly, a GaSb(2 A)/MnSb(A) superlattice showed ferromagnetic ordering up to above 400 K, with a coercive field of 380 Oe at 10 K.
Journal- Korean Physical Society 12/2005; 4721(75). · 0.45 Impact Factor
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ABSTRACT: We have grown Mn-doped V2VI3 single crystals using the temperature gradient solidification method. We report on the structural and magnetic properties of Mn-doped Bi2Te3, Sb2Te3, Bi2Se3, and Sb2Se3 compound semiconductors. The lattice constants of several percent Mn-doped V2VI3 were slightly smaller than those of the undoped V2VI3 due to the smaller Mn atomic radius (1.40 Å) than those of Bi (1.60 Å) and Sb (1.45 Å). Mn-doped Bi2Te3 and Sb2Te3 had ferromagnetic ordering at TC = 10 and 17 K, respectively. However, Mn-doped Bi2Se3 and Sb2Se3 showed spin glass and paramagnetic properties, respectively.
Journal of Applied Physics 05/2005; 97(10):10D324-10D324-3. · 2.17 Impact Factor
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ABSTRACT: We have fabricated Mn-doped chalcopyrite ZnGeAs2 and ZnSnAs2 single crystals using vertical temperature gradient method. We have found out that Mn-doped ZnGeAs2 and ZnSnAs2 sin-gle crystals showed room-temperature ferromagnetism with Curie temperature of 333 and 329 K, respectively.
Journal- Korean Physical Society 03/2003; 422090. · 0.45 Impact Factor
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ABSTRACT: We have grown Mn-doped V 2 VI 3 single crystals using the temperature gradient solidification method. We report on the structural and magnetic properties of Mn-doped Bi 2 Te 3 , Sb 2 Te 3 , Bi 2 Se 3 , and Sb 2 Se 3 compound semiconductors. The lattice constants of several percent Mn-doped V 2 VI 3 were slightly smaller than those of the undoped V 2 VI 3 due to the smaller Mn atomic radius 1.40 Å than those of Bi 1.60 Å and Sb 1.45 Å. Mn-doped Bi 2 Te 3 and Sb 2 Te 3 had ferromagnetic ordering at T C = 10 and 17 K, respectively. However, Mn-doped Bi 2 Se 3 and Sb 2 Se 3 showed spin glass and paramagnetic properties, respectively. © 2005 American Institute of Physics. Group V 2 -VI 3 compounds are known as good materials for room-temperature thermoelectric and thermomagnetic re-frigeration and power generation. Bi 2 Te 3 , Sb 2 Te 3 , and Bi 2 Se 3 are narrow-band gap semiconductors with rhombohedral lay-ered crystal structure; three TeSe–BiSb–TeSe–BiSb– TeSe sequences combine to make a unit cell. 1 They can be cleaved easily along planes perpendicular to the trigonal axis i.e., along the basal planes due to a weak van der Waals bonding between TeSe atoms over a strong covalent bond-ing between BiSb and TeSe layers. On the other hand, Sb 2 Se 3 is a relatively wide-band-gap semiconductor E g = 1.3 eV with orthorhombic crystal structure. 2 Currently diluted ferromagnetic semiconductors, which are prepared by substituting transition metals into nonmag-netic semiconductors, have attracted the worldwide scientific interests for the possible spintronic devices. Ferromagnetism was observed in various systems such as groups II-VI, 3–5 III-V, 6–8 IV, 9,10 II-IV-V 2 , 11 etc. It was also reported that Fe-doped Bi 2 Te 3 and V-doped Sb 2 Te 3 had ferromagneticFM ordering at 12 and 22 K, respectively. 12,13 Here we report on the single crystal growth and mag-netic properties of Mn-doped group V 2 -VI 3 Bi 2 Te 3 , Sb 2 Te 3 , Bi 2 Se 3 , and Sb 2 Se 3 compound semiconductors. Single crystalline Mn-doped V 2 VI 3 were prepared from high-purity 99.999% manganese Mn, bismuth Bi, anti-mony Sb, tellurium Te, and selenium Se powders with particle sizes −200 meshes to maximize the surface area and thereby enhance the reaction kinetics. First, the powders were weighed and loaded into thick walled quartz ampoules. The ampoules were then evacuated 10 −6 Torr and sealed. After encapsulation, the sealed ampoules were mixed, loaded into a vertical furnace, and heated slowly to form single phase. The Bi 2−x Mn x Te 3 was heated to 1130 ° C at 30 °C/h followed by a 120 h soak. For single crystal growth, the temperature was slowly cooled from 1130 ° C to 800 ° C at 1 °C/h and thereafter at 100 °C/h. Sb 2−x Mn x Te 3 , Bi 2−x Mn x Se 3 , and Sb 2−x Mn x Se 3 were cooled from 800 °C to 600 °C at 1 °C/h and thereafter at 100 °C/h. This procedure resulted in single crystals 8 mm in size. The compositions of Mn were determined using electron probe microanalyzer. We have prepared Bi 1.96 Mn 0.04 Te 3 , Sb 1.97 Mn 0.03 Te 3 , Bi 1.97 Mn 0.03 Se 3 , and Sb 1.96 Mn 0.04 Se 3 single crystals. Figure 1 shows the photograph image of Bi 1.96 Mn 0.04 Te 3 single crys-tal. In order to confirm the crystal structures of Bi 1.96 Mn 0.04 Te 3 and Sb 1.96 Mn 0.04 Se 3 , we performed -2 powder x-ray diffraction XRD studies as shown in Fig. 2.
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ABSTRACT: We have grown a 37-period GaSb(25 Å)/MnSb(2 Å) superlattice on GaAs(001) substrate with 1000 Å GaSb buffer layer by solid-source molecular beam epitaxy. We have observed that the streaky RHEED patterns of GaSb and MnSb were maintained even when the growth was finished in 37 periods, indicating the 2-dimensional layer-by-layer growth of MnSb on GaSb or vice versa. Interestingly, a GaSb(25 Å)/MnSb(2 Å) superlattice showed ferromagnetic ordering up to above 400 K with its coercive field of 380 Oe at 10 K.
Science and Technology, 2005. KORUS 2005. Proceedings. The 9th Russian-Korean International Symposium on;
