各向异性磁介质的电感新公式

本文从求在具有对称张量ik的各向异性磁介质中磁场基本方程组的解而得各向异性的磁矢势A的积分公式,并由此导出了标量形式和张量形式的自感系数和互感系数的特性公式以及这两种形式系数之间的变换关系。文中最后以实例对本文导出的新公式进行了验证。     

Revealing Controllable Anisotropic Magnetoresistance in Spin–Orbit Coupled Antiferromagnet Sr2IrO4

Antiferromagnetic spintronics actively introduces new principles of magnetic memory, in which the most fundamental spin‐dependent phenomena, i.e., anisotropic magnetoresistance effects, are governed by an antiferromagnet instead of a ferromagnet. A general scenario of the antiferromagnetic anisotropic magnetoresistance effects mainly stems from the magnetocrystalline anisotropy related to spin–orbit coupling. Here magnetic field driven contour rotation of the fourfold anisotropic magnetoresistance in bare antiferromagnetic Sr₂IrO₄/SrTiO₃ (001) thin films hosting a strong spin–orbit coupling induced J_eff = 1/2 Mott state is demonstrated. Concurrently, an intriguing minimal in the magnetoresistance emerges. Through first principles calculations, the bandgap engineering due to rotation of the Ir isospins is revealed to be responsible for these emergent phenomena, different from the traditional scenario where relatively more conductive state is obtained usually when magnetic field is applied along the magnetic easy axis. These findings demonstrate a new efficient route, i.e., via the novel J_eff = 1/2 state, to realize controllable anisotropic magnetoresistance in antiferromagnetic materials.     

Magnetic susceptibility of (Bi2 ? xSbx)Te3 (0 < x < 1) alloys in the temperature range 2 to 50 K

The superconducting quantum interferometer device with Josephson junctions (SQUID magnetometer) is used to study the temperature dependences of the magnetic susceptibility of (Bi_2−x Sb _x )Te₃ (0 < x < 1) alloy crystals in the temperature range 2 to 50 K, at the magnetic field vector H orientations H | C ₃ and H ⊥ C ₃ with respect to the crystal trigonal axis C ₃. It is found that the magnetic susceptibility of the ion core of the samples under study is χ ^G = −0.35 × 10⁻⁶ cm³/g, the contribution of lattice defects to magnetic susceptibility can be disregarded, and the contribution of free carriers is of a diamagnetic nature in the entire studied temperature range. It is shown that the contribution of free carriers to the resulting magnetic susceptibility and its anisotropy can be described within the Pauli and Landau-Peierls approach. In calculating the magnetic susceptibility, taking into account the constant concentration of free carriers in the state of pronounced degeneracy, it is found that the temperature dependence of the anisotropic effective masses varies with crystal chemical composition. This is possibly associated with the complex structure of the valence band and its variation as the Sb₂Te₃ content in the alloy increases.     

Electromagnetic wave propagation in magnetic multilayers— Non-reciprocal reflections

A theory of EM wave propagation through magnetic multilayers and superlattices is presented based on the propagation matrix of a magnetic film. By using theP matrix, the transmission and reflection coefficients of layered magnetic media, including: (1)semi-infinite magnetic surfaces, (2) magnetic multilayers, (3) semi-infinite magnetic superlattices are obtained. The numerical results show that the EM modes of a magnetic layer system is excited and manifested as the sharp dips in theS-polarized reflection and the dispersion curves of the magnetic polaritons can be measured by a method similar to the attenuated total reflection (ATR) technique. Supported by the National Natural Science Foundation of China     

In-Plane Magnetic Field-Driven Creation and Annihilation of Magnetic Skyrmion Strings in Nanostructures

In bulk chiral crystals, 3D structures of magnetic skyrmions form topologically protected skyrmion strings (SkS) that have shown potential as magnonic nano-waveguides for information transfer. Although SkS stability is expected to be enhanced in nanostructures of skyrmion-hosting materials, experimental observation and detection of SkS in nanostructures under an applied in-plane magnetic field is difficult. Here, temperature-dependent magnetic field-driven creation and annihilation of SkS in B20 FeGe nanostructures (nanowires and nanoplates) under in-plane magnetic field (H_||) are shown and the mechanisms behind these transformations are explained. Unusual asymmetric and hysteretic magnetoresistance (MR) features are observed but previously unexplained during magnetic phase transitions within the SkS stability regime when H_|| is along the nanostructure's long edge, which increase the sensitivity of MR detection. Lorentz transmission electron microscopy of the SkS and other magnetic textures under H_|| in corroboration with the analysis of the anisotropic MR responses elucidates the field-driven creation and annihilation processes of SkS responsible for such hysteretic MR features and reveals an unexplored stability regime in nanostructures.     

Effect of Cu–Al substitution on the structural and magnetic properties of Co ferrites

In this work copper aluminum substituted cobalt nanocrystalline spinel ferrites having general formula Co_1−xCu_xFe_2−x Al_xO₄, with 0.0≤x≤0.8 have been synthesized by using a co-precipitation method. The Cu–Al substituted samples were annealed at 600 °C and characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM). XRD analysis confirmed a single phase spinel structure and the crystalline size calculated using Scherrer׳s formula found to be in the range of 14−24 nm. This crystalline size is small enough to achieve the suitable signal to noise ratio in the high density recording media. The FTIR spectra reveal two prominent frequency bands in the wave number range 350–600 cm⁻¹, which confirm the cubic spinel structure and completion of chemical reaction. Magnetic studies reveal that the coercivity (H_c) attains a maximum value of 1142 Oe at 14 nm. The increasing trend of magnetic parameters (coercivity and retentivity) is consistent with crystallinity. The role played by the Cu–Al ions in improving the structural and magnetic properties are analyzed and understood. The optimized magnetic parameters suggest that the material with composition Co_0.6Cu_0.4Fe_1.6Al_0.4O₄ may have a potential application for high density recording media. Our simple, economic and environmental friendly preparation method may contribute towards the controlled growth of high quality ferrite nanopowder, potential candidates for recording.     

Engineering Large Anisotropic Magnetoresistance in La0.7Sr0.3MnO3 Films at Room Temperature

The magnetoresistance (MR) effect is widely used in technologies that pervade the world, from magnetic reading heads to sensors. Diverse contributions to MR, such as anisotropic, giant, tunnel, colossal, and spin‐Hall, are revealed in materials depending on the specific system and measuring configuration. Half‐metallic manganites hold promise for spintronic applications but the complexity of competing interactions has not permitted the understanding and control of their magnetotransport properties to enable the realization of their technological potential. This study reports on the ability to induce a dominant switchable magnetoresistance in La_0.7Sr_0.3MnO₃ epitaxial films at room temperature (RT). By engineering an extrinsic magnetic anisotropy, a large enhancement of anisotropic magnetoresistance (AMR) is achieved which at RT leads to signal changes much larger than the other contributions such as the colossal magnetoresistance. The dominant extrinsic AMR exhibits large variation in the resistance in low field region, showing high sensitivity to applied low magnetic fields. These findings have a strong impact on the real applications of manganite‐based devices for the high‐resolution low field magnetic sensors or spintronics.     

Anisotropic Strain-Mediated Symmetry Engineering and Enhancement of Ferroelectricity in Hf0.5Zr0.5O2/La0.67Sr0.33MnO3 Heterostructures

Hafnium-based binary oxides have attracted considerable attention due to their robust ferroelectricity at the nanoscale and compatibility with silicon-based electronic technologies. To further promote the potential of Hafnium oxides for practical device applications, it is essential to effectively harness the interplay between structural symmetry, domain configuration, and ferroelectricity. Here, using Hf_0.5Zr_0.5O₂/La_0.67Sr_0.33MnO₃ (HZO/LSMO) heterostructures as a model system, the anisotropic strain-mediated symmetry engineering and ferroelectricity enhancement are systematically investigated. By growing the heterostructures on (110)-oriented perovskite substrates, considerable anisotropic strain is imposed on the LSMO bottom electrodes. Such an anisotropically-strained LSMO layer acts as a structural template and effectively tune the structural symmetry, polar/non-polar phase ratio, and ferroelectricity of the HZO top layer. Specifically, the anisotropic tensile strain stabilizes the ferroelectric rhombohedral and orthorhombic phases, thus enhancing the remnant polarization (P_r) up to 22 µC cm⁻². In contrast, the anisotropic compressive strain facilitates the formation of non-ferroelectric tetragonal phases, leading to a suppressed P_r down to 8 µC cm⁻². These findings provide a guideline for understanding and modulating the intrinsic structure-ferroelectricity relationship of HZO through anisotropic strain-mediated symmetry engineering, which may shed light on the development of hafnium-oxide-based electronic devices.     

Simulation of Electromagnetic Wave Reflection on Plasma by Multiresolution Time-Domain Method

A novel method based on multiresolution time-domain method (MRTD) for dispersive medium is provided, called shift operator MRTD (SO-MRTD).The recurrence formula from D to E of plasma dispersive medium can be gotten by inducting shift operator directly. The conception is perspicuity and conciseness. By using this method, the reflection and transmission coefficient that electromagnetic wave acts on plasma slab are computed. Comparing with analytical solution, it proofs the validity and precision of this algorithm.     

High-frequency heating and dynamic susceptibility of small La1 ? xAgyMnO3 + δ particles in the range of the magnetic phase transition

The nanoparticles of the lanthanum-silver manganites with the general formula La_{1 − x} Ag _y MnO_{3 + δ} (LAMO) that exhibit the Curie temperature T _C in the range 35…50°C, which is important for medical applications, are synthesized and studied. The heating kinetics of the LAMO aqueous suspensions under the action of the high-frequency (HF) magnetic field is experimentally studied and the self-stabilization in the vicinity of the Curie temperature is demonstrated. A sharp increase in the HF-absorption (specific absorption rate) is observed for the materials under study when approaching the Curie temperature from below. This effect is proven by direct measurements of the dynamic magnetic susceptibility in the critical range. The physical interpretations of the HF absorption are based on the hysteresis and oscillations of domain boundaries. It is demonstrated that the materials under study are promising for the medical hyperthermia with controlled heating temperature.     

Enhanced Magnetic Anisotropy and Orbital Symmetry Breaking in Manganite Heterostructures

Manipulating magnetic anisotropy in complex oxide heterostructures has attracted much attention. Here, three interface‐engineering approaches are applied to address two general issues with controlling magnetic anisotropy in the La_2/3Sr_1/3MnO₃ heterostructure. One is the paradox arising from the competition between Mn_3d–O_2p orbital hybridization and MnO₆ crystal field. The other is the interfacial region where the nonuniform Mn? O bond length d and Mn? O? Mn bond angle θ disturb the structural modulation. When the interfacial region is suppressed in the interface‐engineered samples, the lateral magnetic anisotropy energy is increased eighteen times. The d‐mediated anisotropic crystal filed that overwhelms the orbital hybridization causes the lateral symmetry breaking of the Mn 3d_x²_?y² orbital, resulting in enhanced magnetic anisotropy. This is different from the classic Jahn–Teller effect where the lateral symmetry is always preserved. Moreover, the quantitative analysis on X‐ray linear dichroism data suggests a direct correlation between Mn 3d_x²_?y² orbital symmetry breaking and magnetic anisotropy energy. The findings not only advance the understanding of magnetic anisotropy in manganite heterostructures but also can be extended to other complex oxides and perovskite materials with correlated degrees of freedom.     

Analysis of a circular Hall plate with equal finite contacts

The circular Hall plate with four equal finite line contacts, lying symmetrically in respect of two orthogonal axes, is considered. Analytical expressions for the Hall voltage and the Hall mobility in which the finiteness of the contacts and the magnetic field are taken into account, are obtained by applying Schwarz-Christoffel transformations. It is shown that the numerical calculations involved can be reduced to those of regular definite integrals. Furthermore, in the case of not too large contacts, a simple approximative formula has been derived for the product μ_HB of Hall mobility and magnetic induction. It is given in a form directly suited to practical applications.     

Magnetic properties of donors in GaAsP

The magnetic properties of hydrogenic Te donors and bistable,DX-like S donors in GaAS _x P_1-x have been investigated. Te shows an EPR signal after cooling down, both in the dark. The EPR signal from S appears only after illumination. S does not show an EPR signal after cooling down in the dark, but after illumination when the hydrogenic state of this donor is populated. Static magnetic susceptibility measurements show however that the ground state of S in GaAs _x P_1-x is paramagnetic even though it does not produce an EPR signal. This is in agreement with a one-electron ground state of this bistable donor.     

偏转线圈磁场的测量

本文介绍了用双线圈测量偏转磁场的方法。文中首先导出双线圈处于x(或y)轴任意两个位置求算场参数H0、H2、H4的普遍公式。当两个小线圈的灵敏度稍有差异时,该公式仍然有效。利用沿x(或y)轴测得的一系列数据进行回归分析,求得场参数的最佳拟合值,可适用于离轴较远的距离。     

Nanocrystalline Electroplated Cu–Ni: Metallic Thin Films with Enhanced Mechanical Properties and Tunable Magnetic Behavior

Nanocrystalline 3 µm thick Cu_1–xNi_x (0.45 ≤ x ≤ 0.87) films are electrodeposited galvanostatically onto Cu/Ti/Si (100) substrates, from a citrate‐ and sulphate‐based bath containing sodium lauryl sulphate and saccharine as additives. The films exhibit large values of reduced Young's modulus (173 < E_r < 192 GPa) and hardness (6.4 < H < 8.2 GPa), both of which can be tailored by varying the alloy composition. The outstanding mechanical properties of these metallic films can be ascribed to their nanocrystalline nature—as evidenced by X‐ray diffraction, transmission electron microscopy, and atomic force microscopy—along with the occurrence of stacking faults and the concomitant formation of intragranular nanotwins during film growth. Due to their nanocrystalline character, these films also show very low surface roughness (root mean square deviation of around 2 nm). Furthermore, tunable magnetic properties, including a transition from paramagnetic to ferromagnetic behavior, are observed when the Ni percentage is increased. This combination of properties, together with the simplicity of the fabrication method, makes this system attractive for widespread technological applications, including hard metallic coatings or magnetic micro/nano‐electromechanical devices.     

[[2n,n]] Additive quantum error correcting codes

The self-orthogonal condition is analyzed with respect to symplectic inner product for the binary code that generated by [B1 I B2 B3],where Bi are the binary n ×n matrices,I is an identity matrix.By the use of the binary codes that generated by [B1 I B2 B2B1^T],asymptotic good[[2n ,n ]]additive quantum codes are obtained.     

A DISCUSSION ON FRESNEL APPROXIMATION IN PHASE SCREEN MODEL

The Fresnel approximation in phase screen model is discussed and the coherencefunction is derived for k>>k.The application condition for Rino's results is obtained,and it is|▽R_(△N_e)|/R_(△n_e)<<1.     

Guest‐Induced Chirality in the Ferrimagnetic Nanoporous Diamond Framework Mn3(HCOO)6

Chiral magnets are obtained by inclusion of chiral guest molecules into the channels of an achiral nanoporous ferrimagnet consisting of the Mn₃(HCOO)₆ ( 1 ) framework. Insertion of the R or the S enantiomer of 2‐chloropropan‐1‐ol (CH₃C*HClCH₂OH) in the chiral pores of the previously emptied framework (space group P2₁/c) results in the two corresponding chiral solids ( 1R and 1S , space group P2₁), while insertion of a racemic mixture of the two enantiomers retains the achirality of the host for the meso solid ( 1RS , space group P2₁/c). The R guest is ordered in the M channels while the S guest is ordered in the P channels. In contrast, the R guests in the P channels and the S guests in the M channels are disordered on two crystallographic orientations. For the racemic mixture of the two enantiomers in 1RS , random disorder of guests in both channels is observed. Thus, the localization of the guest molecule depends on the nature of the surface to recognize the guest of a particular chirality. The guest inclusion compounds are thermally stable. The 1R and 1S compounds are optically active. All the compounds adopt a ferrimagnetic ground state. Compared to the host framework of 1 without guest, the Curie temperature decreases for both 1R and 1S but increases for 1RS . The additional interactions between the framework and the inserted guest alcohols strengthen the lattice via hydrogen bonds and other electrostatic forces, and it might account for the significant lowering of the lattice contribution as well as the magnetic component to the specific heat capacity upon guest loading.