Magnetic Reorientation Transition Research Articles

Magnetic anisotropy and spin reorientation transition in a TbFe11Ti single crystal (abstract)

Very large discrepancies exist with regard to the spin reorientation transition in TbFe11Ti (see Ref. for a summary of the different results). In this work, this transition is studied by measuring the angular dependence of the parallel (M∥) and perpendicular (M⊥) components of the magnetization to the applied magnetic field in the temperature range of 4.2–330 K and applied magnetic fields ranging from 2 to 15 kOe. This method allows an accurate determination of the easy magnetization direction to be made, i.e., the maximum value of M∥ and the zero value of M⊥. The experimental results have undoubtedly established that the compound is easy plane below 260 K and easy axis above 320 K. Within this intermediate range of temperature the easy magnetization direction lies along a nonmajor symmetry direction making an angle θ with the c axis. This angle depends on the applied magnetic field and the magnetic history of the sample. This fact can be understood on the basis of the existence of a first-order spin reorientation transition at TSR≊320 K from easy axis to easy plane. Within the temperature region 206–320 K both phases (axial and planar) coexist with relative volumes depending on the applied magnetic field and the magnetic history. This gives rise to a macroscopic conical structure. Such behavior has already been observed in DyFe11Ti.

THEORY FOR THE NONLINEAR MAGNETO-OPTICAL RESPONSE AT INTERFACES

Results of an electronic theory for the nonlinear optical response at metallic interfaces are presented. It is shown that nonlinear Kerr-spectra reveal sensitively the atomic, electronic and magnetic structure. The nonlinear Kerr-rotation is generally much larger than the linear one and depends characteristically on the polarization of the incoming light. Thus, magnetic reorientation transitions can be easily detected as well as domain structures and magnetic structures of multilayer films. The second-harmonic-generation (S.H.G.) is polarization dependent, characteristically different for simple metals and transition-metals, and its temperature dependence can be used to study systems not at equilibrium.

Effect of pressure on the magnetic phase transitions in Er2(Fe1 − Mn )14B compounds

We report results on the effect of high pressure on the magnetic order temperature (Tc) and spin reorientation transition temperature (Tsr) of Er2(Fe1 − xMnx)14B compounds (0 < × < 0.3). No simple relation was observed between the pressure changes on the 3d-3d exchange interaction and the pressure effect on anisotropic magnetic properties manifested by the changes on Tsr.

Thermal expansion anomalies of YCo 4B compound

Temperature dependence of YCo 4B compound has been studied by X-ray diffraction method in the temperature range from 78K to 700 K. Anomalous thermal expansions were observed at about 375 K and 150 K, which correspond to the magnetic order-disorder transition and spin reorientation transition respectively.

Dipolar field effect on magnetic field-induced phase transitions

The concept of the intermediate state arising due to the demagnetizing field has been used in order to describe magnetic field-induced first-order reorientation transitions. Special attention is devoted to the nucleation mechanisms and their effect on the magnetization curve.

Magnetic ordering and spin reorientation transitions in hole-doped T′ phases Nd 2− xSr xCuO 4−δ: A μ +SR study

The magnetic properties of the Nd 2− x Sr x CuO 4−δ( x=0.0–0.20) system are studied using muon spin relaxation. The Néel temperature for long range order of the Cu sublattice decreases from 260 K for the formally reduced x=0.03 sample to 60 K for the formally oxidised x=0.10 sample. The formally oxidised x=0.20 sample (4% hole doping) does not order down to 11 K but shows evidence of slowing down of the Cu 2+ spin fluctuations. Two spin reorientation transitions are identified for low Sr 2+ doping, with 5% Sr 2+ doping being sufficient to suppress the transition. It appears that the destruction of magnetic long range order is a necessary but not a sufficient condition for the onset of metallic and superconducting behaviour in the layer cuprates.

Microscopic theory of spin reorientations - heterophase approach and basic model

Abstract A new approach to the description of magnetic reorientation transitions is proposed. Unlike others, this approach allows the consequent microscopic formulation of the problem to be combined with taking into account heterophase states which occur in magnetics and are a mixture of phases with different directions of magnetization. The proposed theory is illustrated by an exactly solved model which is a heterophase generalization of the anisotropic Heisenberg model with long-range interaction.

Metallic Multilayers and Epitaxy

Figure 2. The dependence of the superconducting transition temperature of NbN films grown on three different types of substrates plotted as a function of substrate temperature during deposition. From the paper "Epitaxial Niobium Nitride/Insulator Layered Structures" by J. Talvacchio, J.R. Gavaler, and A.1. Braginski. 18,----,------,----r---..., spacer layer induces order. When spin motions within one film are excited, long range fluctuating dipolar fields are generated, exciting spin motions in neighboring films. Under these conditions, a coherent ground state is obtained for the entire structure. For alternating ferromagnetic and antiferromagnetic films, the application of a magnetic field induces spin reorientation transitions. He values were shown to vary inversely with the member of lattice planes present in each ferromagnetic film, thus suggesting the ability to tailor the structure. Incident electromagnetic energy can excite a soliton response, transmitting the impinging wave through the structure in a resonant mode. This phenomenon can result in a reflecting structure becoming specifically transparent to radiation. Recent studies suggested that increasing the incident power near the resonance level may excite the electron spin system enough to induce a non-linear magnetic susceptability to the applied field. The second session in this symposia was devoted to superconducting multilayer systems fabricated by advanced sputtering techniques. Those presentations covered amorphous metallic multilayers in fractal, quasi periodic and random layering sequences. Another study reported on the first 60 40 20 oL_......._....L._--'-_--l"-_"-----' o

Magnetic structure and spin reorientation transitions in a system of manganese-substituted thulium orthoferrites

Results of magnetic measurements carried out on single crystals of TmFe1-xMnxO3 (x=0, 0.12, 0.21 and 0.33) at temperatures in the region 2-700K and neutron diffraction investigations performed on powder samples at temperatures 80-650K are presented. The compounds are weak ferromagnets at room temperature. For compounds with a lower amount of manganese (x=0.12 and x=0.21) the spin reorientation phase transition GxFz-GzFx is observed as was already reported for pure TmFeO3(x=0). For the compound with x=0.33 a phase transitions sequence unusual for the pure orthoferrites is established. On the temperature dependence of the spontaneous magnetisation along the crystal a axis a compensation point was observed in the case of all compounds investigated. A qualitative explanation of the experimental results is given on the basis of recent theoretical considerations about the influence of Mn3+ doping ions on rare earth orthoferrite properties.