Spin Reorientation Region Research Articles

Signature of spin reorientation in dielectric and magnetic properties of Nd0.5Dy0.5FeO3 thin films

We present an analysis of the thin film Nd0.5Dy0.5FeO3/Si, focusing on its spin reorientation, dielectric, and magnetic characteristics. Exploring spin reorientation involves assessing dielectric and magnetic attributes across temperatures ranging from 2 to 300 K, at different applied frequencies. At temperatures between 34 and 24 K, a spin reorientation phenomenon is observed at a frequency of 10 kHz. As the applied frequency increases, the region of spin reorientation shifts towards higher temperatures. At 2 MHz, this region shifts to the temperature range from 30 to 45 K. This behaviour of the spin reorientation and shift in the spin reorientation region is further validated by AC Susceptibility data. By examining the magnetic order within the antiferromagnetic thin film, this study introduces an innovative approach to magnetic order investigation using dielectric properties.

Magnetic domain structure and spin reorientation process

Abstract The domain structure was investigated in the spin reorientation region on the (100) and (001) planes of Nd2Fe14B and R(Fe, Co)11Ti (R = Tb, Dy) single crystals by means of the magnetooptical Kerr effect. The magnetic phase diagram of a tetragonal magnetic crystal was theoretically calculated and the effect of domain structures on phase transitions is investigated. On the basis of the observed domain configurations and domain wall density calculations, possible models for the volume magnetization distributions in tetragonal magnetic crystals with “easy cone” and “easy plane” anisotropy have been discussed.

Magnetocaloric and heat capacity studies on NdFe0.5Mn0.5O3

The bulk magnetization, magnetocaloric effect, and heat capacity of polycrystalline NdFe0.5Mn0.5O3 have been studied in the temperature range of 1.5–300 K. The magnetic entropy change (ΔSM) shows a peak near 7 K at 100 kOe with a value of ∼7.22 J kg−1 K−1. Another magnetic entropy change is also observed between 0 and 40 kOe near the spin reorientation region of Fe3+/Mn3+ ions (∼45 K), wherein the entropy change gets suppressed with increasing field. The magnetic heat capacity shows a broad hump near the Néel temperature (∼250 K). Around 5 K, a step-like feature in heat capacity due to the Schottky effect is observed which is associated with the crystal field effects in Nd3+ ions.

Features of magnetostriction behavior of the intermetallic compound Sm0.2Y0.8Fe2 near the spin reorientation transitions

The structural and magnetic properties of Sm0.2Y0.8Fe2 intermetallic compound are investigated using X-ray diffraction and magnetic measurements and compared with the properties of the SmFe2 compound. It is established that the partial substitution of Y for Sm in SmFe2 leads to the decrease in both the Curie temperature TC and the two spin-reorientation transition temperatures TSR1 and TSR2. The complex behavior of the field and temperature dependencies of the longitudinal, transversal, anisotropic and volume magnetostriction in a wide temperature range (including the spin-reorientation region) is discussed in terms of the single-ion anisotropy and magnetostriction theory. The influence of other factors, such as peculiarities of the state of Sm3+ ions and competition between contributions to magnetostriction from the iron and samarium sublattices, is also considered.

Studies on structural and magnetic properties of NdFeO3 single crystals grown by optical floating zone technique

NdFeO3 single crystals have been grown by optical floating-zone technique using Nd2O3 and Fe2O3 as the source by solid-state reaction method. The crystalline structure of NdFeO3 belongs to orthorhombic symmetry and the presence of a distorted perovskite structure was confirmed by powder X-ray diffraction (XRD) analysis. From the XRD results, it is visualized that the lattice expansion has been observed in the unit cell parameters which may appear due to interstitial defects in the NdFeO3 matrix. The deficiency of oxygen atoms and the presence of excess Fe ions in NdFeO3 have been confirmed with EDX spectra. The spin-reorientation region (T = 120 K) exhibits lower coercive field and the hysteresis loops depict enhanced magnetization (Ms and Mr) values of NdFeO3 single crystal. Presence of compensation temperature point at Tcomp = 7.5 K denotes the anti-parallel alignment of rare-earth ions with Fe magnetic moments. At high temperatures, Fe3+ magnetic moments show strong antiferromagnetic interactions ensuing in Neel temperature (TN) at 690 K.

Evolutions of acoustic and optical mode resonances in the spin reorientation Permalloy film

We investigate the static and dynamic magnetic properties of a wedge Permalloy film. The spin distribution of the wedge film depends on the film thickness, ranging from the homogeneous in-plane to the out-of-plane component. The spin reorientation region of the wedge film is determined by using a magnetic force microscopy and magneto-optical Kerr effect measurements as well as the micromagnetic simulation. The dynamic properties of the spin distribution depending on the thickness are investigated by the microwave method. The acoustic and optical mode resonances of the wedge film are controlled by changing the direction of the microwave magnetic field and the stripe domains. The resonance frequency could be influenced by its domain structure and reveals the different anisotropies of the film. The results show that the spin distribution of the stripe domain depending on the thickness can be used to control the spin dispersion and precession frequency of the film for high-frequency applications.

Spontaneous Spin Reorientation in Gd–Co Amorphous Films

The phenomenon of spontaneous spin reorientation in Gd–Сo amorphous films, which results from the competition between the perpendicular magnetic anisotropy and shape anisotropy, is studied. It is shown that the reorientation occurs via the formation of a fine-grained nonuniform magnetic structure called hypercritical state in a wide temperature range. Magnetic domains in the spin-reorientation region are characterized using magnetic and magneto-optical measurements. Based on the experimental magnetometric data and results of simulating the temperature dependences of spontaneous magnetization, the phase diagram of the films containing 16–26 at % Gd is constructed, which, being plotted on coordinates elemental composition—temperature, exhibits the ranges of existence of the perpendicular anisotropy, transition magnetic anisotropy (hypercritical state), and planar magnetization state.

The order of magnetic phase transitions in disordered double perovskite oxides Sm2FeCoO6 and Dy2FeCoO6

We present the results on the order of phase transition around the spin re-orientation region using isothermal magnetization data performed on the sol-gel synthesized disordered double perovskite oxides Sm2FeCoO6 and Dy2FeCoO6 by Arrott plot method. The temperature variation of the DC magnetization data of both the samples show that there are two magnetic phase transitions; one at high temperature regime, the conventional paramagnetic (PM) to ferro or ferrimagnetic (FM or FIM) and the other at low temperatures, ferro or ferrimagnetic (FM or FIM) to antiferromagnetic (AFM). From the Arrott plot method, it is inferred that spin re-orientation transitions of both the compounds has a first order nature corresponding to the FM (FIM) to AFM transition.

Single crystal growth, magnetic and thermal properties of perovskite YFe0.6Mn0.4O3 single crystal

High quality YFe0.6Mn0.4O3 single crystal was grown by floating zone technique using a four-mirror-image-furnace under flowing air. Powder X-ray diffraction gives well evidence that the specimen has an orthorhombic structure, with space group Pbnm. Temperature dependence of the magnetizations of YFe0.6Mn0.4O3 single crystal were studied under ZFC and FC modes in the temperature range from 5K to 400K. A clear spin reorientation transition behavior (Γ4→Γ1) is observed in the temperature range of 322–316K, due to the substitution of Mn at the Fe site of YFeO3. Its Néel temperature is around 385K. Moreover, the spin reorientation is verified by the change of magnetic hysteresis loops of the sample along [001] axis in the temperature range of 50–385K. The thermal properties of the sample were measured by the differential scanning calorimeter (DSC) from 300K to 500K, which also clearly appear anomaly in the spin reorientation region.

Conventional and anisotropic magnetic entropy change in HoAl2 ferromagnetic compound

In this paper, we present theoretical investigations on the conventional and anisotropic magnetocaloric effects in the cubic HoAl2 ferromagnetic compound. They are investigated in terms of a Hamiltonian that takes into account the Zeeman and exchange magnetic interactions, and crystalline electric field. In this study we have explored recent experimental results in HoAl2 single crystals and polycrystalline samples. HoAl2 presents a spin reorientation transition at 20K and different signatures of this phenomenon are reproduced in our calculations. In addition, we have calculated the anisotropic variation of magnetic entropy that corresponds to a rotation of a HoAl2 single crystal from its [110] towards its [100] direction in the presence of a constant applied magnetic field. The intensity of the anisotropic effect is twice that one of the conventional effect at spin reorientation region. A subtle signature of the spin reorientation is also observed in the [111] direction. We conclude that the crystal electric field term plays the principal role to describe the main magnetic characteristics of the system, not being necessary to include in the Hamiltonian others effects such as elastic or high order magnetic interactions.

Spin reorientation transition process in single crystal NdFeO3

The spin reorientation transition in single crystal NdFeO3 is studied using AC magnetic susceptibility, hysteresis loops, and polarized terahertz (THz) time domain spectroscopy measurements. Different frequency dependence behaviors of AC susceptibility reflect that the dynamic response of magnetization inside the spin reorientation region differs from the phase outside the transition region. The magnetization hysteresis loops at different temperatures reveal that domains formed during the spin reorientation process, which coincides with the abrupt increase of AC magnetic susceptibility during the transition. In addition, temperature dependent THz wave excitation of quasi-antiferromagnetic mode indicates the process of spin reorientation as a continuous rotation of Fe3+ spins rather than a mixed phase of Γ4 and Γ2.

Cluster-glass behavior correlated with spin reorientation in Yb1−x Pr x FeO3

The magnetic properties of polycrystalline Yb1−xPrxFeO3 (0≤x≤0.9) are systematically investigated. A cusp in the zero-field-cooled dc magnetization and a frequency-dependent peak in the ac susceptibility reveal the glassy behaviors in this system. Interestingly, for YbFeO3, the freezing temperature Tf is just in the narrow spin-reorientation region of single-crystal YbFeO3 reported previously. The frequency-dependent peak in the real part of the ac susceptibility can be described by critical slowing down of spin dynamics. The fit to this critical slowing down law yields the values τ0=2.79×10−7 s and zv=2.61. The value of τ0 is in good agreement with values found in cluster-glass systems. Anomalous thermal hysteresis in the field-cooled magnetization is found in all samples, with a crossover point between the field-cooled cooling and field-cooled warming curves. These anomalous thermal hysteresis behaviors are explained by the competing interaction between the iron-ion subsystem and rare-earth-ion subsystem.

Laser-induced ultrafast spin dynamics in ErFeO3

Using 100-fs optical laser pulses, we have been able to excite and probe spin dynamics in the rare-earth orthoferrite ${\mathrm{ErFeO}}_{3}$. The investigation was performed in a broad temperature range with the focus on the vicinities of the compensation point ${T}_{\mathrm{comp}}\ensuremath{\approx}47\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and the spin reorientation transition region in the interval $86\phantom{\rule{0.16em}{0ex}}\mathrm{K}\ensuremath{\lesssim}T\ensuremath{\lesssim}99\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Spin precession excited by the laser pulse was present in a large part of the investigated temperature range, but was especially strong near the spin reorientation region. In this region the laser pulse also caused an ultrafast spin reorientation. By changing the laser pulse fluence, we could vary both the reorientation amplitude and the reorientation speed. We show that the laser-induced spin dynamics in ${\mathrm{ErFeO}}_{3}$ is caused in part by heating and in part by the inverse Faraday effect. Comparing to the results of similar experiments in other rare-earth orthoferrites, we found the speed of the laser-induced spin reorientation to be significantly lower. We attribute this finding to the weaker electron-phonon coupling of the ${\mathrm{Er}}^{3+}$ 4f electrons with the lattice.

Magnetic properties of NdFeO3 single crystal in the spin reorientation region

High quality NdFeO3 single crystal has been grown by the four-mirror image floating zone technique. The magnetic properties and specific heat of NdFeO3 single crystal were systematically studied in the temperature range from 2 to 300 K. A clear spin reorientation behavior is observed in a wide temperature range from 100 to 170 K, with the gradual transition of the Fe3+ magnetic moment ordering from {Gz, Mx}-type ordering at low temperatures to {Gx, Mz}-type ordering at high temperatures. In the temperature range from 170 to 300 K, the value of Mx is not equal to zero. It is assumed a single {Gx, Mz}-type ordering mixed with {Gxz, Mxz}-type orderings. During the spin orientation transition process, the hysteresis loops become narrow with very small coercivity. Based on the specific heat measurement, the Schottky anomaly at very low temperature and the thermal anomalies induced by the spin reorientation were also discussed.

Giant Rotating Magnetocaloric Effect in the Region of Spin-Reorientation Transition in theNdCo5Single Crystal

We have investigated the anisotropy of the magnetocaloric effect in a NdCo₅ single crystal in a wide range of temperatures, including the spin-reorientation temperature region. In the field μ(0)H =1.3 T in the spin-reorientation region 250-310 K, we discovered a giant rotating magnetocaloric effect of ~ 1.6 K, caused by rotation of the magnetization vector. The calculations of the anisotropy magnetocaloric effect for the field μ(0)H =1.3 T have been carried out.

Spin reorientation process in Er2Fe14C magnetic material

The Er 2 Fe 14 C intermetallic compound has been synthesized and studied by 57 Fe Mössbauer spectroscopy and differential scanning calorimetry (DSC). The spin reorientation phenomenon was investigated in this compound in the temperature range 80–330 K by narrow step temperature scanning in the neighborhood of the reorientation temperature 316 K. Spin arrangement in this compound was determined. Experimental Mössbauer spectra were analyzed by fitting six Zeeman subspectra according to six iron occupations of the crystallographic sublattices, except for spin reorientation region, where each subspectrum splits additionally into two Zeeman sextets. A consistent description of Mössbauer spectra below, during and above the spin reorientation temperature – was established. Parameters of hyperfine interactions, their temperature dependencies in transition region and spin reorientation temperature were obtained from consistent fits. DSC studies proved that the spin reorientations were accompanied by thermal effects. The spin reorientation temperature was established to be T SR = 313 ± 2 K and the enthalpy of the transition Δ H = 0.26 ± 0.04 J/g. A comparison of spin reorientation process in Er 2 Fe 14 C and Er 2 Fe 14 B is presented.

Manipulation of spin reorientation transition of ultrathin Co films by using an artificially roughened Pd(111) substrate

The authors present a simple method to control the spin reorientation transition (SRT) in ultrathin Co films using an artificially roughened substrate prepared by ion bombardment with varying the incident angle φ from 0° to 80°. The combined study of surface magneto-optical Kerr effects and scanning tunneling microscopy revealed a drastic increase of the onset thickness of the SRT (tc) by up to 41% for the substrate sputtered at φ=80°, whereas there is an 18% reduction for the φ=20° sample relative to the SRT in the smooth surface. The second- and fourth-order surface anisotropies (K2s and K4s) responsible for the drastic change in the SRT are determined from a theoretical fit to the magnetization orientation in the spin reorientation region.

Structural properties of TmFeO3 in the spontaneous reorientation region

X-ray studies of TmFeO3 single crystals in the spontaneous spin-reorientation region demonstrate the absence of lattice distortions and no lowering of the symmetry of the crystal from rhombic to monoclinic and thus confirm the purely magnetic nature of the Γ2–Γ24–Γ4 spin reorientation in orthoferrites.

Structural properties ofErFeO3in the spin-reorientation region

In spin-reorientation transition in orthoferrites the temperature dependence of the magnetization differs from that predicted by conventional mean-field theory. One of the explanations of this discrepancy is based on the assumption that structural changes accompany magnetic transitions. Recently we proposed an explanation of this phenomena based on purely magnetic grounds. In this x-ray study a possible structural change in an $\mathrm{Er}\mathrm{Fe}{\mathrm{O}}_{3}$ single crystal is probed. Our measurements find no lattice distortions in the spin-reorientation region, thus supporting the purely magnetic nature of spin rotation.

Spin reorientation and structural changes inNdFeO3

The crystal structure and the Fe3+ magnetic moment ordering in NdFeO3 have been studied by high-resolution neutron powder diffraction at temperaturesranging from 1.5 to 300 K. Between 100 and 200 K a spin reorientationtransition is observed with gradual changes of the directions of theFe3+ ordered magnetic moments. The spin reorientation temperaturerange is associated with changes of the crystal structure. Theb latticeparameter has a broad local minimum in the spin reorientation region. There is also a coherent rotationof the FeO6 octahedra with an increase of the Fe–O–Fe angles with increasing temperature.These structural changes tend to increase the strength of the in-plane(a,b) Fe–Fe interactions and to decrease the strength of Fe–Fe interactions along thec-axis as the temperatureincreases. The Fe3+ magnetic moment ordering above 200 K is close to the antiferromagneticGx type.The total Fe3+ ordered magnetic moment at room temperature equals3.87(5) μB. Below100 K the Fe3+ magnetic moment ordering is a combination of the antiferromagneticGx andGz type. The orderedFe3+ magnetic momentcomponents at 1.5 K are Mx = 1.30(15) μB and Mz = 3.97(5) µB. There is a C-type antiferromagnetic ordering of theNd3+ magnetic moments at 1.5 K with the orderedNd3+ momentvalue of 1.10(7) μB.