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1.
A.W. Rushforth K. Výborný K.W. Edmonds C.T. Foxon A.C. Irvine K. Olejník Jairo Sinova B.L. Gallagher 《Journal of magnetism and magnetic materials》2009,321(8):1001-1008
We present details of our experimental and theoretical study of the components of the anisotropic magnetoresistance (AMR) in (Ga,Mn)As. We develop experimental methods to yield directly the non-crystalline and crystalline AMR components which are then independently analysed. These methods are used to explore the unusual phenomenology of the AMR in ultra thin (5 nm) (Ga,Mn)As layers and to demonstrate how the components of the AMR can be engineered through lithography induced local lattice relaxations. We expand on our previous [A.W. Rushforth, et al., Phys. Rev. Lett. 99 (2007) 147207] theoretical analysis and numerical calculations to present a simplified analytical model for the origin of the non-crystalline AMR. We find that the sign of the non-crystalline AMR is determined by the form of the spin-orbit coupling in the host band and by the relative strengths of the non-magnetic and magnetic contributions to the impurity potential. 相似文献
2.
Giddings AD Khalid MN Jungwirth T Wunderlich J Yasin S Campion RP Edmonds KW Sinova J Ito K Wang KY Williams D Gallagher BL Foxon CT 《Physical review letters》2005,94(12):127202
We report a large tunneling anisotropic magnetoresistance (TAMR) in (Ga,Mn)As lateral nanoconstrictions. Unlike previously reported tunneling magnetoresistance effects in nanocontacts, the TAMR does not require noncollinear magnetization on either side of the constriction. The nature of the effect is established by a direct comparison of its phenomenology with that of normal anisotropic magnetoresistance (AMR) measured in the same lateral geometry. The direct link we establish between the TAMR and AMR indicates that TAMR may be observable in other materials showing room temperature AMR and demonstrates that the physics of nanoconstriction magnetoresistive devices can be much richer than previously thought. 相似文献
3.
R. A. Konchakov N. P. Kobelev V. A. Khonik A. S. Makarov 《Physics of the Solid State》2016,58(2):215-222
The characteristic values of the elastic polarizability tensor components of point defects in crystalline and amorphous copper, which determine changes in the elasticity tensor components upon introduction of defects, have been found using the molecular dynamics method. A relation of the elastic polarizability tensor with the main parameter of the interstitialcy theory, i.e., shear susceptibility, has been established. An analysis of the elastic polarizability tensors of defects in crystalline and amorphous copper has demonstrated that, in a noncrystalline structure, there are specific atomic configurations that under deformation manifest themselves similarly to elastic dipoles (interstitial atoms in a dumbbell configuration) in single-crystal copper. 相似文献
4.
Anomalous anisotropic magnetoresistance in single-crystalline Co/SrTiO3(001) heterostructures
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Shuang-Long Yang 《中国物理 B》2021,30(12):127302-127302
The anisotropic magnetoresistances (AMRs) in single crystalline Co(6 nm)/SrTiO3(001) heterostructures from 5 K to 300 K with the current direction setting along either Co[100] or Co[110] are investigated in this work. The anomalous (normal) AMR is observed below (above) 100 K. With the current along Co[100] direction, the AMR shows negative longitudinal and positive transverse magnetoresistances at T< 100 K, while the AMR is inverse with the current along Co[110]. Meanwhile, the amplitude ratio between Co[110] and Co[100] is observed to be as large as 29 at 100 K. A crystal symmetry-adapted model of AMR demonstrates that interplay between the non-crystalline component and crossed AMR component results in the anomalous AMR. Our results may reveal more intriguing magneto-transport behaviors of film on SrTiO3 or other perovskite oxides. 相似文献
5.
Pawan Kumar R. PrasadR.K. Dwivedi H.K. Singh 《Journal of magnetism and magnetic materials》2011,323(21):2564-2568
A comparative study of the out-of-plane anisotropic magnetoresistance (AMR) in single crystalline and polycrystalline thin films of phase separated manganite Nd0.51Sr0.49MnO3 has been carried out. On-axis DC magnetron sputtering was used to deposit the single crystalline films (30 and 100 nm in thickness) on single crystal (0 0 1) LaAlO3 (LAO) and polycrystalline films (100 nm) on (1 0 0) Yttrium-stabilized ZrO2 (YSZ) substrates. The in-plane and out-of-plane magnetotransport properties of these films differ significantly. A large low field AMR is observed in all the films. AMR shows a peak below the insulator-metal transition temperature in the single crystalline films, while the same increases monotonically in the polycrystalline film. Relatively larger low field AMR (∼20% at T=78 K and H=1.7 kOe) in the polycrystalline films suggests the dominance of the shape anisotropy. 相似文献
6.
7.
J. Murin 《Czechoslovak Journal of Physics》1981,31(1):62-71
The theory of the second moment of NMR spectra of oriented partially crystalline polymers is developed in this paper. Two phase model of the structure of polymer is considered in deriving of second moment of NMR spectra. Possibilities of characterization of the degree of orientation of macromolecular chains separately in crystalline and noncrystalline regions of the polymer are discussed in this paper. 相似文献
8.
《Physica E: Low-dimensional Systems and Nanostructures》2011,43(10):2685-2689
In-plane magnetic anisotropy of 40-μm-long (Ga,Mn)As wires with different widths (0.4, 1.0, and 20 μm) has been investigated between 5 and 75 K by measuring anisotropic magneto-resistance (AMR). The wires show in-plane 〈1 0 0〉 cubic and [−1 1 0] uniaxial anisotropies, and an additional lithography-induced anisotropy along the wire direction in narrow wires with width of 0.4 and 1.0 μm. We derive the temperature dependence of the cubic, uniaxial, and lithography-induced anisotropy constants from the results of AMR, and find that a sizable anisotropy can be provided by lithographic means, which allows us to control and detect the magnetization reversal process by choosing the direction of the external magnetic fields. 相似文献
9.
Binary ferromagnetic Mn(3-delta)Ga (1.2<3-delta< or =1.5) crystalline thin films have been epitaxially grown on wurtzite GaN(0001) surfaces using rf N-plasma molecular beam epitaxy. The film structure is face-centered tetragonal with CuAu type-I (L1(0)) ordering with (111) orientation. The in-plane epitaxial relationship to GaN is nearly ideal with [110](MnGa) parallel[1100](GaN) and [112](MnGa) parallel[1120](GaN). We observe magnetic anisotropy along both the in-plane and out-of-plane directions. The magnetic moments are found to depend on the Mn/(Mn+Ga) flux ratio and can be controlled by observation of the surface reconstruction during growth, which varies from 1x1 to 2x2 with increasing Mn stoichiometry. 相似文献
10.
Frenkel AI Ehre D Lyahovitskaya V Kanner L Wachtel E Lubomirsky I 《Physical review letters》2007,99(21):215502
Although neither SrTiO3 nor BaZrO3 has any polar crystalline polymorphs, they may form noncrystalline pyro- and piezoelectric phases [Adv. Mater. 19, 1515 (2007)10.1002/adma.200602149]. These phases and the similar phase of BaTiO3 have been called quasiamorphous. In this Letter, the structure of the quasiamorphous phase of SrTiO3 is examined by the x-ray absorption fine structure technique and found to be built of a random network of polar octahedral TiO6 local bonding units. While in crystalline SrTiO3 all TiO6 octahedra are apex sharing only, in its amorphous and quasiamorphous phases, some octahedra share edges. The polarity of the quasiamorphous phase is due to the partial alignment of the TiO6 octahedra. Such a mechanism is completely different from that of inorganic polar crystals. This mechanism should be possible in a large variety of other compounds that contain similar local bonding units. 相似文献
11.
X. B. Chen M. X. Li K. Li Y. Feng S. Z. Bi G. Y. Zhang Y. G. Sun 《Optics Communications》1999,160(4-6):364-375
Up-conversion luminescence phenomenon of crystalline and noncrystalline ErP5O14 induced by about 650 nm laser are researched and analysed carefully. Not only two-photon but also three-photon up-conversion luminescence are found. The up-conversion mechanism of crystalline ErP5O14 is mainly the nonresonant up-conversion energy transfer, which is mainly achieved directly through a kind of coupling state of quasi-clusters of rare-earth ions and do not exchange the phonon energy with the crystal-lattice base to offset the energy mismatch. The mechanism, to our best knowledge, has not been reported yet. 相似文献
12.
报道了快速循环晶化Bi和Ba代替DyIG磁光膜的实验结果,发现在累加退火时间小于3分钟时(温度650~680℃)膜内部存在非晶区域和沿厚度晶化不均匀现象。导出晶相与非晶相界面法拉第角计算公式。计算结果表明,界面效应导致膜整体法拉第效应减弱。 相似文献
13.
Naonori Yoshioka Yutaka Obata Hiromichi Kawai 《Journal of Macromolecular Science: Physics》2013,52(3):567-585
Two kinds of relaxation mechanisms in semicrystalline polymers, i.e., the primary relaxation mechanism attributed to the noncrystalline phase and the crystalline relaxation mechanism attributed to the crystalline phase, are explained, respectively, in terms of (1) a modified Bueche's model of a one-dimensional vibrating string taking higher-order potential effects into account and (2) Montroll's model of a plane lattice in the form of a vibrating membrane. The modified Bueche's theory of a one-dimensional vibrating string gives a slope in the wedge portion of the relaxation time spectrum of less than – 1/2, when one assumes that the force constants of higher-order potential effects of intra- and intermolecular interaction are negative. The plane lattice model of a membrane vibrating in a lateral as well as in a longitudinal fashion gives a box-type relaxation time spectra over almost the same relaxation time range. 相似文献
14.
Takashi Manago Kazuya Kanazawa Tatsuya Kera 《Journal of magnetism and magnetic materials》2009,321(15):2327-2330
The anisotropic magneto-resistance (AMR) contributions of a zigzag-shaped NiFe wire were investigated. The magneto-resistance (MR) behaviors in different magnetic-field directions clearly reflect the angular relationships between the directions of the current and magnetic moment in the subdivisions. The resistance in remanence after magnetization along 0° in respect to the longer direction of zigzag was larger than that along 90°. Assumed that the difference appears due to the AMR contribution in the domain wall trapped at the corner, the MR ratio was estimated to be 1.2%, which is in good agreement with the AMR of the NiFe film. We clearly showed that the domain-wall resistance originates in the AMR. 相似文献
15.
Robert J. Samuels 《Journal of Macromolecular Science: Physics》2013,52(1-2):41-82
A quantitative determination has been made of the structural elements which control deformation and shrinkage processes in isotactic polypropylene fibers and films. It is found that strain processes such as fabrication draw and shrinkage are controlled by the noncrystalline region of this highly crystalline polymer. Quantitative structure-property correlations are obtained for the polymer, which reveal the interactions between temperature, strain, and orientation. The thermal activation energy of the noncrystalline chains is also determined from these solid-state structure measurements. 相似文献
16.
Ping Wang 《Journal of computational physics》2010,229(5):1573-1599
In this paper we report an efficient numerical method combining a staggered arbitrary Lagrangian Eulerian (ALE) formulation with the adaptive mesh refinement (AMR) method for materials modeling including elastic–plastic flows, material failure, and fragmentation predictions. Unlike traditional AMR applied on fixed domains, our investigation focuses on the application to moving and deforming meshes resulting from Lagrangian motion. We give details of this numerical method with a capability to simulate elastic–plastic flows and predict material failure and fragmentation, and our main focus of this paper is to create an efficient method which combines ALE and AMR methods to simulate the dynamics of material responses with deformation and failure mechanisms. The interlevel operators and boundary conditions for these problems in AMR meshes have been investigated, and error indicators to locate material deformation and failure regions are studied. The method has been applied on several test problems, and the solutions of the problems obtained with the ALE–AMR method are reported. Parallel performance and software design for the ALE–AMR method are also discussed. 相似文献
17.
B. Riscob M. Shakir N. Vijayan V. Ganesh G. Bhagavannarayana 《Applied Physics A: Materials Science & Processing》2012,107(2):477-484
The effect on crystalline perfection, second harmonic generation (SHG) efficiency, optical transparency and mechanical properties
due to Mn(II) doping in KDP single crystals grown by slow evaporation solution technique by adding different quantities of
MnCl2 in the solution has been investigated. The actual incorporated quantity of Mn(II) in the crystals was evaluated by atomic
absorption spectroscopy. Powder XRD study confirms the crystal system of KDP and found no additional phases at all doping
levels (1 to 5 mol%). The influence of Mn(II) doping on the crystalline perfection has been assessed by high-resolution XRD
and these studies revealed that the grown crystals could accommodate Mn(II) in the interstitial positions of the crystalline
matrix of KDP only up to some critical concentration, above which the crystal developed structural grain boundaries. The relative
SHG efficiency of the crystals was found to be increased sharply at low concentrations (1 mol%), and above this value it was
decreased as the concentration increases though it is still higher than that of pure KDP. UV-Vis studies also revealed the
same behavior with a significant enhancement at 1 mol% concentration and later gradually decreased. Good increment in the
hardness values has been observed by increasing the doping concentrations. 相似文献
18.
19.
High-resolution transmission electron microscopy and bulk magnetometry study of LaFe11.5Si1.5 compound
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This paper studies the microstructural and magnetic properties of LaFe11.5Si1.5 compound by means of high-resolution transmission electron microscope and bulk magnetometry measurements. The crystalline structure is accompanied with the noncrystalline and nanocrystalline structures. This characteristic is the reflection of the crystalline process held by quenching. The inverse susceptibilities diverge and deviate from Curie-Weiss law under low applied magnetic fields. This paper proposes the possible mechanism between the anomalous susceptibilities and microstructure, and offers a perspective on the magnetic properties of metastable intermetallic compounds. 相似文献
20.
理论预言窄禁带稀磁半导体(Ga,Mn)Sb及其异质结构可能存在量子反常霍尔效应等新奇特性, 近年来受到了特别关注. 但是, 由于(Ga,Mn)Sb薄膜生长窗口窄, 纯相(Ga,Mn)Sb薄膜制备比较困难, 迄今关于这类材料的研究报道为数不多. 本文采用低温分子束外延的方法, 通过优化生长条件, 成功制备出厚度为10 nm, Mn含量在0.016至0.039之间的多组(Ga,Mn)Sb薄膜样品. 生长过程中反射式高能电子衍射原位监测和磁性测量都表明没有MnSb等杂相的偏析, 同时原子力显微镜图像表明其表面形貌平滑, 粗糙度小. 通过生长后退火处理, (Ga,Mn)Sb薄膜的最高居里温度达到30 K. 此外, 本文研究了霍尔电阻和薄膜电阻随磁场的变化关系, 在低温下观测到明显的反常霍尔效应. 相似文献