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28 Feb 2000

Volume 76, Issue 9, pp. 1083-1210

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Strain-dependent vacuum annealing effects in La0.67Ca0.33MnO3−δ films

J. R. Sun, C. F. Yeung, K. Zhao, L. Z. Zhou, C. H. Leung, H. K. Wong, and B. G. Shen

Appl. Phys. Lett. 76, 1164 (2000); http://dx.doi.org/10.1063/1.125971 (3 pages) | Cited 52 times

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The effects of vacuum annealing on the structural and transport properties of the La0.67Ca0.33MnO3−δ films grown on SrTiO3 (LCMO/STO) and NdGaO3 (LCMO/NGO) substrates have been studied. A lattice expansion due to oxygen release during the annealing is observed. Under the same condition, the change of the out-of-plane lattice parameter in LCMO/STO is two to three times larger than that in LCMO/NGO, indicating a strong tendency for the oxygen in the former to escape. Correspondingly, the metal-to-semiconductor transition shifts to lower temperatures, linearly with lattice constant until a critical value, Δd = 0.03 Å for LCMO/STO and Δd = 0.05 Å for LCMO/NGO, after which a sudden drop of the transition temperature to zero occurs. The different lattice strains in both films are presumably responsible for the different critical oxygen contents for the occurrence of the resistive transition. © 2000 American Institute of Physics.
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68.55.-a Thin film structure and morphology
75.47.Gk Colossal magnetoresistance
75.47.De Giant magnetoresistance
81.40.Rs Electrical and magnetic properties related to treatment conditions
81.40.Gh Other heat and thermomechanical treatments
61.72.Cc Kinetics of defect formation and annealing
72.60.+g Mixed conductivity and conductivity transitions
71.30.+h Metal-insulator transitions and other electronic transitions
61.66.Bi Elemental solids
61.66.Dk Alloys

Exciton spin polarization in magnetic semiconductor quantum wires

O. Ray, A. A. Sirenko, J. J. Berry, N. Samarth, J. A. Gupta, I. Malajovich, and D. D. Awschalom

Appl. Phys. Lett. 76, 1167 (2000); http://dx.doi.org/10.1063/1.125972 (3 pages) | Cited 10 times

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Electron-beam lithography and wet etching techniques are used to laterally pattern ZnSe/(Zn,Cd,Mn)Se single quantum wells into magnetically active quantum wires with widths ranging from 20 to 80 nm. Photoluminescence spectroscopy as a function of wire width reveals a competition between elastic strain relaxation and quantum confinement. Magnetophotoluminescence measurements at low temperatures indicate a strong exciton spin polarization due to the sp–d exchange-enhanced spin splitting, ranging from 20% to 60% at 4 T. © 2000 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.20.Ls Magneto-optical effects
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.35.Ji Excitons in magnetic fields; magnetoexcitons
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
81.05.Dz II-VI semiconductors
85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning

Magnetocrystalline anisotropy of TbFe12−xTix single crystals

Jianli Wang, Guangheng Wu, Ning Tang, Dong Yang, Fuming Yang, F. R. de Boer, Y. Janssen, J. C. P. Klaasse, E. Brück, and K. H. J. Buschow

Appl. Phys. Lett. 76, 1170 (2000); http://dx.doi.org/10.1063/1.125973 (3 pages) | Cited 3 times

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TbFe12−xTix single crystals have been investigated by means of magnetic measurements. With decreasing temperature, a spin-reorientation transition from easy axis to easy plane occurs. The rate of decrease of spin-reorientation temperature with x is about −380 K/Ti. There exists a strong magnetocrystalline anisotropy in the basal plane. The anisotropy field Ba between [100] and [110] for the compound TbFe11.15Ti0.85 is as high as 35 T which is about three times Ba in the axial direction. With increasing x, the easy magnetization direction at low temperatures in the basal plane changes from [110] for x = 0.85 to [100] for x = 1.0. The composition dependence of anisotropy can be understood in terms of a change of the crystal field parameters Anm due to substitution of Ti for Fe. © 2000 American Institute of Physics.
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75.30.Gw Magnetic anisotropy
75.40.-s Critical-point effects, specific heats, short-range order
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
71.70.Ch Crystal and ligand fields
75.10.Dg Crystal-field theory and spin Hamiltonians

Ultrasonic study on charge ordering, magnetic, and structural changes in La0.25Ca0.75Mn0.93Cr0.07O3

X.-G. Li, H. Chen, C. F. Zhu, H. D. Zhou, R. K. Zheng, J. H. Zhang, and L. Chen

Appl. Phys. Lett. 76, 1173 (2000); http://dx.doi.org/10.1063/1.125974 (3 pages) | Cited 15 times

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The longitudinal and transverse ultrasonic velocities and attenuations, the transport and magnetic properties, as well as the structural changes of polycrystalline La0.25Ca0.75Mn0.93Cr0.07O3 have been studied systematically. A velocity minimum and an attenuation peak for both longitudinal and transverse waves occur around the temperature Tco of charge ordering transition accompanied by the structural change from a cubic to a tetragonal phase. Near temperature TN (where the c-axis length shows a maximum), the sharp decrease of velocities for both waves and the appearance of a longitudinal attenuation peak are attributed to the antiferromagnetic transition together with the anomalous change in c-axis length of the tetragonal phase. The simultaneous occurrence of the ultrasonic, lattice, charge ordering, magnetic, and transport anomalous characteristics indicates the strong electron–phonon and spin–phonon interactions in the system. © 2000 American Institute of Physics.
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62.65.+k Acoustical properties of solids
75.50.Dd Nonmetallic ferromagnetic materials
64.70.K- Solid-solid transitions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
63.20.K- Phonon interactions
71.38.-k Polarons and electron-phonon interactions

Ferromagnetic resonance detection with a torsion-mode atomic-force microscope

Markus Löhndorf, John Moreland, and Pavel Kabos

Appl. Phys. Lett. 76, 1176 (2000); http://dx.doi.org/10.1063/1.125989 (3 pages) | Cited 11 times

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We have developed a ferromagnetic resonance (FMR) instrument based on a torsion-mode atomic-force microscope (AFM). The instrument measures the torque on a magnetized thin film in a static out-of-plane field perpendicular to the film surface. The magnetic film is deposited onto an AFM microcantilever. FMR measurements are performed at a fixed microwave frequency of 9.15 GHz with a sweeping in-plane field. At the FMR condition, the change in the average in-plane magnetization of the film is at a maximum corresponding to a maximum change in the torque on the AFM cantilever. Our instrument is capable of measuring fluctuations of in-plane magnetization of 63.3 A/m of NiFe film samples with a total volume of 1.1×10−10 cm3. Given a signal-to-noise ratio of 40, we estimate a magnetic moment sensitivity of 1.7×10−16 A/m2.
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76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
07.79.Lh Atomic force microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
75.70.Ak Magnetic properties of monolayers and thin films
07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
61.05.Qr Magnetic resonance techniques; Mössbauer spectroscopy (for structure determination only)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.80.+q Magnetomechanical effects, magnetostriction

Photocontrol of spin-glass state in Mg1.5FeTi0.5O4 spinel ferrite films

Y. Muraoka, H. Tabata, and T. Kawai

Appl. Phys. Lett. 76, 1179 (2000); http://dx.doi.org/10.1063/1.125975 (3 pages) | Cited 13 times

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A spin-glass state up to 210 K has been found in (Mg, Fe){Mg,Fe,Ti}2O4 spinel ferrite thin films formed on α-Al2O3(0001) substrates. The films exhibit long-time relaxation of the magnetization in zero-field-cooled operation below 210 K; also, the ac susceptibility measurements show the presence of frequency-dependent cusp temperature. Both of the above observations are characteristic features of a spin glass. The change of magnetic state in the films from a spin glass to ferrimagnet has been achieved over a wide temperature range below 160 K by means of light irradiation. © 2000 American Institute of Physics.
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75.50.Lk Spin glasses and other random magnets
75.50.Gg Ferrimagnetics
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Cr Saturation moments and magnetic susceptibilities
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