Magnetization reorientation in HoCo2

In order to confirm the magnetization reorientation in HoCo₂, torque measurements have been performed at various temperatures on a spherical single crystal, in the (001) and (011) planes. The easy magnetization direction is the [110] axis at 4.2 K and the [100] axis above 16 K. Furthermore, between 11 K and 16 K, the easy magnetization direction rotates progressively within the (001) plane. These results agree with the magnetization measurements and can be interpreted by a crystal field model.     

Spin reorientation and magnetization anomaly in Er2Fe14B and Tm2Fe14B

Static magnetic measurements have been carried out on single crystals of Er₂Fe₁₄B and Tm₂Fe₁₄B in a temperature range between 77 and 590 K. Spin reorientation phenomena have been found in both compounds slightly above room temperature. In Er₂Fe₁₄B, the easy direction of magnetization changes from [100] to [001] at 316 K as temperature increases, and Tm₂Fe₁₄B from [100] to [001] at 310 K. Anomalously large anisotropy in the saturation magnetization has been detected around the spin reorientation temperature.     

Magnetic anisotropy of Sm2Fe14B single crystal

Magnetization measurements have been made on a Sm₂Fe₁₄B single crystal in magnetic fields up to 140 kOe. The easy direction of the magnetization lies along [100] in the tetragonal structure P4₂/mnm. Magnetic anisotropy energies at 290K along [110] and [001] have been estimated to be 5.8×10⁶ and 1.1×10⁸ erg/cm³, respectively, both becoming much larger at lower temperature. No evidence of the spin canting of Nd₂Fe₁₄B type is observed even at 4.2K.     

Magnetic reversal of the ferroelectric polarization in a multiferroic spinel oxide

Ferroelectric transition has been detected in a ferrimagnetic spinel oxide of CoCr2O4 upon the transition to the conical spin order below 25 K. The direction [110] of the spontaneous polarization is normal to both the magnetization easy axis [001] and to the propagation axis [110] of the transverse spiral component, in accord with the prediction based on the spin-current model. The reversal of the spontaneous magnetization by a small magnetic field (approximately 0.1 T) induces the reversal of the spontaneous polarization, indicating the clamping of the ferromagnetic and ferroelectric domain walls.     

Spin reorientation transition in (111) textured L10 CoPt layers

In this work, a spin reorientation transition from [001] axis to an in-plane direction occurs near Curie temperature under a small external field for (111) textured L1₀ CoPt layers in an AlN/CoPt multilayer film, indicating the dominant role of the shape anisotropy at elevated temperatures over the magnetocrystalline anisotropy. A large in-plane residual magnetization is also observed after cooling the sample from a temperature above the Curie point. The formation of magnetization during cooling is considered due to the alignment of magnetic moments along the easy axis by the small field in the spin reorientation transition temperature region. Our work reveals the importance of shape anisotropy for the formation of magnetization in the heat assisted magnetic recording process.     

Magnetic properties of A DyNi2 single crystal

Magnetic measurements have been performed on a single crystal of DyNi₂ in applied fields up to 135 kOe. In the ferromagnetic range (T_c = 25 K), the easy magnetization direction is [100] and the hardest one is [111]. Crystal field parameters have been determined from the field and temperature dependence of the magnetization measured along the three principal axes. A two-dimensional model has been used to take into account the rotation of magnetization towards the field. The deduced parameters are W = -0.8 K and x = 0.49. The corresponding anisotropy is very large: especially even a field of 135 kOe applied along a difficult magnetization axis cannot rotate the magnetization along this direction.     

Magnetic anisotropy in the paramagnetic phase of TbAl2

The magnetic anisotropy of a single crystal of TbAl₂ has been measured by torque magnetometry from below the Curie point up to 170 K, well into the paramagnetic phase. Within a (110) plane the torque can be described by the expression L(θ) = {P sin 2θ} H² + {Q sin 2θ + S sin 4θ} H⁴ + {T sin 4θ} H⁶, where θ is the an gle formed by the magnetization vector with a [001] axis. The first term (in H²) is interpreted as produced by arrays of defects with axial symmetry. The second (in H⁴) and third (in H⁶) terms arise from anisotropic fourth and sixth rank tensor paramagnetic susceptibilities. On the other hand if the anisotropy is described in terms of effective conventional anisotropy constants K₁ and K₂ within the temperature range 90–170 K it is found that both constants change continuously across the Curie temperature and furthermore the [111] direction remains the easy direction in the paramagnetic range. Anisotropy measurements reveal themselves as a sensitive indicator of the level of macroscopic defects in magnetic crystals.     

Magnetic anisotropy and spin-reorientation in HoAl2

Torque measurements have been performed at several temperatures and magnetic fields, on a single crystal of HoAl₂ in the (1 1 0) plane. The easy magnetization direction changes from the [1 0 0] to [1 1 0] near T_R = 20 K in magnetic fields between 0.2 and 1.6 T. At temperatures below T_R a new non-major cubic symmetry easy direction appears which rotates with temperature in the plane of the sample. This behaviour and that of the complete torque curves have been interpreted on the basis of a single ion model.     

Er2(Fe1-xCox)15Ga2化合物的磁晶各向异性

通过X射线衍射和磁性测量等手段研究了Er₂(Fe_1-xCo_x)₁₅Ga₂化合物的结构与磁性，重点讨论了它们的磁晶各向异性.实验结果表明，Er₂(Fe_1-xCo_x)₁₅Ga₂化合物均为Th₂Ni₁₇型六角结构，晶格常数a,c和单胞体积V随Co含量的 关键词：     

Changes of easy axis during the magnetization of dysprosium

Changes in the easy axis of magnetization of dysprosium, within the basal plane, between 77 and 160 K and in applied fields up to 1.25 T, reported by Bly et al. [1] have been reinvestigated and some inconsistencies have been resolved. Changes were only confirmed above 132 K, where the b axis is easy just above the critical field. On increasing the applied field the basal plane anisotropy dies away reappearing with the a axis easy. The changeover occurs at field and temperature values very close to those where a magnetoresistance anomaly has been observed by Akhavan et al. [2]. It is shown that this change may be explained in principle, without any change in the crystal field, by the narrowing of a fan-like spin structure occurring as an intermediate phase between the helical anti-ferromagnetic and the ferromagnetic phases. Between 77 and 110 K anomalies in torque curves in low fields are attributed to domain processes.     

Tb0.3Dy0.7(Fe0.9T0.1)1.95合金的结构、自旋重取向和穆斯堡尔谱

系统研究了室温下Tb_0.3Dy_0.7(Fe_0.9T_0.1)_1.95(过渡金属元素T=Mn，Fe，Co，B，Al，Ga)合金中ⅢA族金属和过渡金属元素T替代Fe对结构、自旋重取向和穆斯堡尔谱的影响.结果发现，不同金属T替代Fe，Tb_0.3Dy_0.7(Fe_0.9T_0.1)_1.95，合金具有相同的MgCu₂型立方Laves相结构；Al，Ga替代使Tb_0.3Dy_0.7(Fe_0.9T_0.1)_1.95合金的易磁化方向在{110}面逐渐偏离了立方晶体的主对称轴，即自旋重取向，B，Mn，Co替代未使易磁化轴发生明显转动；Al，Ga元素替代使超精细场H_hf略有下降，B，Mn替代对超精细场H_hf的影响不大，而Co元素替代使超精细场H_hf有较大增加；所有元素替代使同质异能移IS有所增加；B，Al，Ga和Mn替代使四极劈裂Q_s增加，而Co替代使四极劈裂Q_s下降. 关键词： 立方Laves相 自旋重取向 穆斯堡尔谱     

Ho2Fe14B化合物的高场磁化过程

基于单离子模型,详细分析了Ho₂Fe₁₄B化合物在T=0K沿[100],[110]和[001]轴磁化时,Ho和Fe次晶格的磁化过程。预测了该化合物在T=0K高达2000 kOe的磁场中沿主晶轴的磁化曲线。 关键词：     

Metamagnetic states in single crystal HoNi<Subscript>2</Subscript>B<Subscript>2</Subscript>C at <Emphasis Type="Italic">T</Emphasis> ≈ 1.9 K: Torque magnetometry study

Metamagnetic transitions in single-crystal rare-earth nickel borocarbide HoNi₂B₂C have been studied at T ≈ 1.9 K with a Quantum Design torque magnetometer. With increasing field, transitions to antiferromagnetic, ferrimagnetic, non-collinear, and saturated paramagnetic states take place. The critical fields of the transitions depend crucially on the angle θ between applied field and the easy axis [110]. Measurements of torque along the c axis have been made while changing the angular direction of the magnetic field (parallel to basal tetragonal ab planes) and with changing field at fixed angle over a wide angular range. Two new phase boundaries in the region of the non-collinear phase have been observed, and the direction of the magnetization in this phase has been precisely determined. At low field the antiferromagnetic phase is observed to be multidomain. In the angular range around the hard axis (?6° ≤ ? ≤ 6°, where ? is the angle between the field and hard axis [100]) the magnetic behavior is found to be “frustrated” with a mixture of phases with different directions of the magnetization.     

Magnetic properties of V5S8 single crystals

The magnetic properties of V₅S₈ single crystals have been investigated by susceptibility and torque measurements. The susceptibilities parallel and perpendicular to the magnetic easy axis show a remarkable anisotropy below the Neel temperature of 32 K and are nearly Isotropie above that temperature. The easy axis is found to be nearly along the c-axis of the monoclinic lattice, being inclined at an angle of 9.6 ± 1.0° from the c-axis toward the a-axis. The torque curves, measured up to 24.4 kOe at liquid helium temperature, deviate from the usual form of a sine function with increasing magnetic field. The analysis of these torque curves suggests that spin flopping may occur at 43 kOe, a comparatively low critical field. Using these experimental results, a localized d-electron model for a particular site of the vanadium-ion, proposed by previous investigators, is examined.     

Magnetostriction relative to pretransition in Ni50.5Mn24.5Ga25 single crystal

The strain behaviors as well as the structural and magnetic changes relative to the pretransition in the Ni_50.5Mn_24.5Ga₂₅ single crystals have been characterized by various methods, such as pretransition strain, magnetostriction, magnetization measurements, and TEM observations. A large magnetostriction up to 505 ppm measured in the [001] direction of the sample is obtained at the pretransition temperature with only a low magnetic field of about 1 kOe applied along the [010] direction. We found that not only the pretransition strain pronounces a more large change, but also the magnetostriction at a certain temperature exhibits a more large magnitude for field applied along the [010] direction than with field along the [001] direction. It is concluded that the magnetoelastic interaction is responsible for the premartensitic transition, and the magnetoelastic interaction in the [010] direction is stronger than that in the [001] direction.     

Magnetostriction of antiferromagnetic FeGe2

The anisotropic magnetostriction of FeGe₂ is measured for magnetic field along the [1 0 0] and [1 1 0] axes at temperature 4.2 K and along [1 0 0] from 77 to 300 K. The behaviour is consistent with spin reorientation in the basal plane. The saturation magnetostriction and the characteristic field required to produce saturation decrease with increasing temperature and approach zero at the lower transition temperature, $\text{T}{}_{\mathrm{K}}\text{? 265}$ K. This suggests that the spins flip from the basal plane into the direction of the tetragonal [0 0 1] axis at T_K.     

Sm2(TM)17合金的磁性(自旋再取向相变)研究

本文研究了Sm₂(FeNiCoM)₁₇合金(M为非磁性组元)的磁性。样品由六角结构无序型的2∶17主相及少量FeNi合金杂相组成。在六角结构的e轴方向(易磁化方向)观察到下述异常现象:低温(273K以下)时的磁化及反磁化曲线发生明显的跃变,跃变时相应的磁场H_r随温度下降而增大;磁滞迴线是蜂腰型的,温度愈低蜂腰愈明显;升温时磁化强度随温度变化(1.5K至居里点T_C)的曲线上出现极大值,其相应的温度T_t随磁场增大而降低;降温时观察到了热磁滞后现象。但在基面(难磁化方向)上及Co含量增多(>18at％)时,样品却表现了正常的铁磁行为。本文提出用磁矩非共线结构排列的自旋再取向相变来解释上述异常现象,并给出自旋倒向所需越过的能垒高度U=9.2×10^-15erg,用设想磁结构的模型得到的磁化强度的计算值与实验值也符合得较好。 关键词：     

The magnetic properties and anisotropy of the linear chain compound TlFe3Te3

The magnetic properties of TlFe₃Te₃ are studied on powdered samples and single crystals. Below 220 K TlFe₃Te₃, is a very anisotropic ferromagnet, the crystallographic c axis being the easy axis of magnetization. While in the easy direction saturation is achieved below 0.5 kOe, in the hard direction saturation is reached at 64 kOe. The angular dependence of the magnetization follows closely a cos ¦?¦ law. The magnetic transition is very abrupt at low external fields, suggesting a first order phase transition. It is accompanied by a small anomaly in the thermal dilatation of the c axis. The magnetization shows an anomalous increase below 50 K suggesting a phase transition.     

First order magnetization process in Pr2Fe14B single crystal

High-field magnetization process in Pr₂Fe₁₄B single crystal has been studied in static magnetic fields up to 230 kOe. The spontaneous magnetization is along the [001] direction of the tetragonal structure down to 1.5 K. When the field is applied along the [100] and [110] directions at low temperatures, magnetization jumps are observed at about 130 kOe and 160 kOe, respectively, which are considered to correspond to the first order magnetization process (FOMP). Observed features of the magnetization curves including FOMP and their temperature dependence are well reproduced by the calculation based on a simplified Hamiltonian including the crystalline electric fields and the FePr     

Spin reorientation in Tm2Fe14B

The magnetic structures of Tm₂Fe₁₄B above and below its spin reorientation temperature (approx. 316 K) have been determined from high resolution neutron powder diffraction measurements.Within experimental accuracy all magnetic moments lie in the basal plane at 294 K and along the c-axis at 340 K. The Tm and Fe moments are antiparallel.