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The motion of a domain wall in a magnetic film with an antidot array leads to the formation of a vortex magnetization reversal zone moving along the sample. A description of the magnetization dynamics in the film is obtained by micromagnetic simulations based on the Landau-Lifshitz-Gilbert equation for various film thickness and hole arrangement and size. We show that the magnetization reversal zone either passes through the antidot array or "freezes" on it. Using a special technique for visualizing vortex structures, based on the calculation of topological charges of two types, we establish the relationship between the magnetization dynamics and the types of vortex structures.

Although coercivity is one of the fundamental properties of permanent magnets, it has not been well understood. In this paper, micromagnetics and thermal activation magnetization reversal theories are briefly reviewed, and then our recent macroscopic and microscopic experimental approaches for thermally activated magnetization reversal in advanced Nd-Fe-B hot-deformed magnets are explained. Our experimental results are well supported by the recent atomistic spin model calculations. Moreover, the systematic micromagnetics simulation study makes much clearer the physical picture of the thermally activated magnetization reversal process in permanent magnets., Graphical abstract

Some features of the magnetization reversal of Fe–3% Si sheet electrotechnical steel with different degrees of texturing have been studied. It was revealed that stripe samples, even with the very sharp edge texture {110}〈001〉 have a nonuniform magnetic permeability along the length of the stripe. It is established that this nonuniformity is due to the different sizes of crystallites and different orientations of their magnetization Is with respect to the rolling direction of the studied samples. It is demonstrated that, to decrease the magnetic losses of anisotropic electrotechnical steel via the artificial reduction of its domain structure, it is reasonable to deposit locally strained zones not onto the entire sample surface but only onto areas with the maximum magnetic permeability.

The R-dependent structural and magnetic properties of the disordered RFe0.5Cr0.5O3 (R = Ce, Pr, Nd, Sm) ceramics are systemically investigated. Based on the model composed of the paramagnetic R sub...

In this paper, we consider synthetic antiferromagnetic (SAF) structures and their influence in a fixed layer of a spin-tunnel junction on the magnitude of the magnetoresistive effect and temperature stability. The SAF structure consists of two ferromagnetic (FM) layers, between which a nonmagnetic film is located. The ion exchange interaction of two FM layers has an oscillating character and depends on the nonmagnetic layer thickness and the surface roughness of the FM layers. The mechanism of SAF magnetization reversal with fixation by an antiferromagnetic layer and in its absence, as well as the effect of the sequence of deposition of layers in the SAF structure on its properties, are considered. The main applications of SAF structures as a part of spintronic devices is described.

We have investigated magneto-structural phase transitions in polycrystalline YVO3 using high-resolution neutron powder diffraction toward understanding the phenomenon of magnetization reversal. Contrary to earlier reports, our study reveals that both C-type and G-type antiferromagnetic ordering, corresponding to G-type and C-type orbital ordered phases, respectively, occur at the same temperature (TN = 115 K) with the G-type antiferromagnetic phase growing at the expense of the C-type one on cooling. These processes cease at TS ∼ 77 K; however, a minor (∼4%) untransformed C-type phase remains unchanged down to 1.7 K. The symmetry analysis indicates different symmetry origins of the Dzyaloshinskii-Moriya interaction in each phase, which can explain the magnetization reversal observed between TN and TS. We discuss that magnetic phase separation and associated weak ferromagnetism may be the common mechanism underlying the magnetization reversal phenomenon observed in other RVO3 systems (R = rare earth).

Ordered ferromagnetic nanowire arrays are widely studied due to the diversity of possible applications. However, there is still no complete understanding of the relation between the array’s parameters and its magnetic behavior. The effect of vortex states on the magnetization reversal of large-diameter nanowires is of particular interest. Here, we compare analytical and micromagnetic models with experimental results for three arrays of iron nanowires with diameters of 33, 52 and 70 nm in order to find the balance between the number of approximations and resources used for the calculations. The influence of the vortex states and the effect of interwire interactions on the remagnetization curves are discussed. It has been found that 7 nanowires treated by a mean field model are able to reproduce well the reversal behavior of the whole array in the case of large diameter nanowires. Vortex states tend to decrease the influence of the structural inhomogeneities on reversal process and thus lead to the increased predictability of the system.

In pyrochlore iridates, nontrivial magnetic domain walls (DWs) carrying ferromagnetic (FM) moments were recently uncovered despite their bulk all-in-all-out (AIAO) antiferromagnetic (AFM) configura...

The origin of low coercivity of high La–Ce-containing Nd–Fe–B sintered magnets was analyzed based on characterization of the microstructure, magnetic domain structure, and magnetization reversal process. It can be found that the coercivity of magnet decreases sharply and the ratio value of coercivity (Hcj) to anisotropic field (HA) is below the theoretical value when the amount of La–Ce substitution for Nd is more than 40 wt%. The grain boundaries with poor magnetic isolation in the high La–Ce-containing Nd–Fe–B sintered magnets play an important role in reducing the coercivity of the magnet. In addition, a larger proportion of the reversible portions can be found for the magnet with a large content of La–Ce, which will lead to the low performance of the magnet.

We have comprehensively investigated asymmetric magnetization reversal behaviors of (x-A Co/7.7 A Pt)5 multilayers (x = 3.1 and 4.7) with perpendicular magnetic anisotropy. Our direct observation of magnetic domain structures by means of magneto-optical microscopy reveals that the asymmetry arises both from nucleation and wall-motion processes. An asymmetric nucleation behavior is observed, which could be originated from the preexisting non-reversed domains which might have a reproducible or random spatial distribution, controllable by tuning the field profile. An asymmetric wall-motion behavior stemming from asymmetric stripe domain evolution is also observed.

Electric-field control of magnetization reversal is promising for low-power spintronics. Here in a magnet/insulator nanoheterostructure which is the fundamental unit of magnetic tunneling junction in spintronics, we demonstrate the electric field induced 180$$^ \circ $$ magnetization switching through a multiscale study combining first-principles calculations and finite-temperature magnetization dynamics. In the model nanoheterostructure MgO/Fe/Cu with insulator MgO, soft nanomagnet Fe and capping layer Cu, through first-principles calculations we find its magnetocrystalline anisotropy linearly varying with the electric field. Using finite-temperature magnetization dynamics which is informed by the first-principles results, we disclose that a room-temperature 180$$^ \circ $$ magnetization switching with switching probability higher than 90% is achievable by controlling the electric-field pulse and the nanoheterostructure size. The 180$$^ \circ $$ switching could be fast realized within 5 ns. This study is useful for the design of low-power, fast, and miniaturized nanoscale electric-field-controlled spintronics.

In this paper, the magnetization reversal of sphere-shaped ferromagnetic nanoparticles has been investigated by means of micromagnetic simulation. Some ferromagnetic particles such as Cobalt, Iron, Nickel, and Permalloy were modeled with size variation from 50 nm to 100 nm. The discretization of the ferromagnetic model was used a cell size of 2.5×2.5×2.5 nm3 considering the exchange length (lex) of the materials. The quasi-static magnetic field was induced into the nanosphere to observe the magnetization response under time dependence. It is found that the coercivity values are decreased as the sphere size increased, which was conformed the experimental results. It is also observed that the domain structure of a single particle in remanent and ground-state condition are identical. Therefore, the specific understanding of magnetization process and domain structures in ferromagnetic nanoparticles could be an important step in the development of nanopatterned magnetic memory storage.

Magnetization reversal of a hard/soft magnetic bilayer in an external magnetic field has been studied by the Monte Carlo method. The magnetization reversal curves of a magnetic bilayer have been built at various thicknesses of the soft magnetic layer. The effects of the intralayer exchange interaction and the anisotropy constant of the soft magnetic layer on the magnetization reversal have been studied, too. The phase diagrams of the magnetic bilayer are presented.

Shape- and thickness-dependent magnetization reversal process is investigated in CoFe nanostructures by micromagnetic simulations. The reversal is abrupt in the case of 10-nm and 20-nm thick rectangular and square nanostructures. Intermediate double vortex states are formed in rectangular nanostructures of thickness 30 to 60 nm when the field is applied along the longer dimension. Magnetization reversal along the shorter dimension happens through the formation of multivortex states. Similar type of reversal is observed in 40 to 60-nm thick square nanostructures of dimensions 225 nm and 335 nm.

Using the soft X-ray magnetic circular dichroism (XMCD) technique, we investigated the magnetic states of the Sm 4f and the Mn 3d moments in a Neel N-type ferrimagnet, SmMnO3, which exhibits a striking magnetocapacitive effect around the compensation temperature (Tcomp ≈ 9.4 K). The XMCD results show that the Sm 4f and the Mn 3d moments were always aligned antiparallel to each other and that, upon sweeping a magnetic field, the angular momenta of Sm 4f and Mn 3d were simultaneously reversed at the field where the magnetocapacitive effect was observed. This indicates that the magnetocapacitive effect of SmMnO3 is induced by a simultaneous reversal of Sm 4f and Mn 3d angular momenta, i.e., magnetization reversal. We discuss a plausible origin of the magnetocapacitive effect in terms of the p-d hybridization mechanism.

In the present work, the thermal properties and crystallization process and kinetics of the as-spun Pr6Fe78B16 are thoroughly investigated. The activation energies Ec(x) of crystallization for the Pr2Fe14B phase increase rapidly first and then increase slowly to a maximum value 440 kJ/mol at the crystallization value of 40%, while the Ec(x) of Fe3B phase is mostly lower at the stage of crystallization and then increases gradually with the increase of crystallization fraction. Meanwhile, the enhanced magnetic properties (Hcj, 215 kA/m; Mr, 116 A m2/kg; and (BH)max, 73.9 kJ/m3) have been obtained for the alloy with the annealing temperature at 660 °C. The results of magnetization reversal behavior show that a stronger exchange-coupling interaction between the hard and soft phases can be obtained by the proper annealing temperature.

In this letter we study magnetization reversal and transformation of magnetic domain structures in glass-covered magnetic microwires. Studies were performed using the magneto-optical Kerr effect technique in the presence of the combination of tension and torsion mechanical stresses. Formation and reversible transformations of the surface helical structure, induced by the combined stress, were found. Comparative analysis of the magnetic domain images and hysteresis curves gives unambiguous explanation of the character of the magnetization reversal. Spiral and elliptic structures, as basic helical structures, exist in microwires depending on the values and direction of the applied stresses.

Magnetic nanomaterials are of great interest due to their potential use in data storage, biotechnology, or spintronic based devices, among others. The control of magnetism at such scale entails complexing the nanostructures by tuning their composition, shape, sizes, or even several of these properties at the same time, in order to search for new phenomena or optimize their performance. An interesting pathway to affect the dynamics of the magnetization reversal in ferromagnetic nanostructures is to introduce geometrical modulations to act as nucleation or pinning centers for the magnetic domain walls. Considering the case of 3D magnetic nanowires, the modulation of the diameter across their length can produce such effect as long as the segment diameter transition is sharp enough. In this work, diameter modulated Fe67Co33 ferromagnetic nanowires have been grown into the prepatterned diameter modulated nanopores of anodized Al2O3 membranes. Their morphological and compositional characterization was carried out by electron-based microscopy, while their magnetic behavior has been measured on both the nanowire array as well as for individual bisegmented nanowires after being released from the alumina template. The magnetic hysteresis loops, together with the evaluation of First Order Reversal Curve diagrams, point out that the magnetization reversal of the bisegmented FeCo nanowires is carried out in two steps. These two stages are interpreted by micromagnetic modeling, where a shell of the wide segment reverses its magnetization first, followed by the reversal of its core together with the narrow segment of the nanowire at once.

Here, we study the effect of the Dzyaloshinskii-Moriya interaction (DMI) on magnetic nuclei expansion in Pt/Co/Ir/Co/Pt perpendicular synthetic ferrimagnets. Magnetization reversal is explored as a response to the DMI, affecting the expansion of the magnetic nuclei. We report a nontrivial inverted dependence of the velocity of the double domain wall on the in-plane (IP) magnetic field. This effect is due to competition of the DMI contributions, resulting in effective fields of different signs in the two Co layers. We report a macroscopic manifestation of the DMI as magnetization reversal accelerated by the applied IP magnetic field. Accelerated magnetic relaxation is provided by the DMI-induced ellipticity of the magnetic nuclei, the spreading of which is accompanied by an enhanced number of nuclei contacts in comparison with round nuclei in the absence of an IP field. The obtained results clarify how the DMI contributes to macroscopic magnetic relaxation in the presence of the interlayer Heisenberg exchange interaction in synthetic ferrimagnets with perpendicular anisotropy.

Multi-segmented bilayered Fe/Cu nanowires have been fabricated through the electrodeposition in porous anodic alumina membranes. We have assessed, with the support of micromagnetic simulations, the dependence of fabricated nanostructures’ magnetic properties either on the number of Fe/Cu bilayers or on the length of the magnetic layers, by fixing both the nonmagnetic segment length and the wire diameter. The magnetic reversal, in the segmented Fe nanowires (NWs) with a 300 nm length, occurs through the nucleation and propagation of a vortex domain wall (V-DW) from the extremities of each segment. By increasing the number of bilayers, the coercive field progressively increases due to the small magnetostatic coupling between Fe segments, but the coercivity found in an Fe continuous nanowire is not reached, since the interactions between layers is limited by the Cu separation. On the other hand, Fe segments 30 nm in length have exhibited a vortex configuration, with around 60% of the magnetization pointing parallel to the wires’ long axis, which is equivalent to an isolated Fe nanodisc. By increasing the Fe segment length, a magnetic reversal occurred through the nucleation and propagation of a V-DW from the extremities of each segment, similar to what happens in a long cylindrical Fe nanowire. The particular case of the Fe/Cu bilayered nanowires with Fe segments 20 nm in length revealed a magnetization oriented in opposite directions, forming a synthetic antiferromagnetic system with coercivity and remanence values close to zero.

The causes of reversible variation of coercivity in alloys for permanent magnets as a result of cyclic heat treatments are analyzed including the effect of magnetostatic interaction between microvolumes on the processes of magnetization reversal and on the magnitude of the reversibility of the coercivity. A scheme of the processes occurring in alloys of the Sm – Co – Cu – Fe – Zr system is suggested, which makes it possible to explain logically the mechanism of the “damage – restoration” phenomenon.

The Wiegand wire is known to exhibit a unique feature of fast magnetization reversal in the magnetically soft region accompanied by a large Barkhausen jump. We clarified a significant difference between the magnetization reversals at the surface and at the entire cross section of a Wiegand wire. We conducted magnetization measurements based on the magneto-optical Kerr effect and applied conventional methods to determine the magnetization curves. The switching field of the magnetization reversal at the surface was greater than that at the initiation of a large Barkhausen jump. Our analysis suggests that the outer surface layer exhibits low coercivity.

We have explored the impact of elevated growth and annealing temperatures on the local interfacial structure of thin Fe(12 nm)/Pt(10 nm) spintronic bilayers, epitaxially grown on MgO (100), and their correlation to magnetization reversal and dynamics. Electron-beam evaporation growth and subsequent annealing at 450 °C causes significant roughening of the MgO/Fe interface with irregular steps and multilevel (100) MgO surface terraces. Consequently, threading dislocations emerging at the step edges propagated in the Fe layer and terminated at the Fe/Pt interface, which appears pitted with pits 1.5–3 nm deep on the Fe side. Most of the pits are filled with the overlying Pt, whereby others by ferrimagnetic Fe3O4, forming nanoparticles that occupy nearly 9% of the Fe/Pt interfacial area. Fe3O4 nanoparticles occur at the termination sites of threading dislocations at the Fe/Pt interface, and their population density is equivalent to the density of threading dislocations in the Fe layer. The morphology of the Fe/Fe3O4/Pt system has a strong impact on the magnetization reversal, enhancing the coercive field and inducing an exchange bias below 200 K. Furthermore, low-temperature spin pumping and inverse spin Hall effect voltage measurements reveal that below their blocking temperature the nanoparticles can influence the spin current transmission and the spin rectification effects.

In this study, the magnetic properties, coercivity mechanism, and magnetization reversal process were investigated for Ce-(Y)-Pr-Fe-B films. After the addition of Y and subsequent heating treatment, the formations of REO (RE ≡ Ce and Pr) and REFe2 (RE ≡ rare earths) phases are inhibited, and the microstructure of Ce-Y-Pr-Fe-B film is optimized. Meanwhile, the coercivity and the squareness of the hysteresis loop are significantly improved. The coercivity mechanism of Ce-Y-Pr-Fe-B film is determined to be a mixture of nucleation and pinning mechanisms, but dominated by the nucleation mechanism. The demagnetization results show that the nucleation of reversal magnetic domains leads to irreversible reversal. Our results are helpful to understand the coercivity mechanism and magnetization reversal of permanent magnetic films with multi-main phases.

The technical devices which allow to significantly extend the time range of the studied pulsed magnetization and magnetization reversal processes of magnets that are, e.g., plates, flat films (ferrite-garnet films with easy-plane anisotropy, iron borate monocrystals), along with ensuring measurements of maximum accuracy are considered.

Study of the interlayer interactions and hysteresis processes was performed for the nano/microcrystalline bilayer ribbon composed of soft magnetic Fe73.5Cu1Nb3Si13.5B9 layer and semihard magnetic Co72.5Si12.5B15 layer. Precursor amorphous ribbons were prepared by modified double-nozzle planar flow casting method. Measurement of the First Order Reversal Curves (FORCs) was utilized for detailed characterization of its magnetic hysteresis behaviour. Calculated switching field distribution (SFD) consists of two distinct peaks, each representing specific magnetic phase. With decreasing reversal field value, SFD peak of the microcrystalline, semihard magnetic Co-based layer is shifted to the higher field values, indicating presence of strong positive exchange interaction. On the other hand, SFD peak of the soft magnetic nanocrystalline Fe-based layer is shifted to lower and even negative field values. Such behaviour was associated with the presence of magnetostatic bias field originating in the semihard magnetic layer.

It is shown that a material having four stable positions of the orientation of the magnetization vector makes it possible to double the density of magnetic recording (for example, in MRAM devices) without substantial modifications of production process. This finding is based on investigations of the time aspects of the 180° pulse magnetization reversal of ferrite–garnet films with planar anisotropy, in the region of external fields where the mechanism of uniform rotation of magnetization operates.

A method is proposed for measuring the coercive force using a U-shaped electromagnet with a gap between the electromagnet poles and the test sample. It is demonstrated that the device can operate in a dynamic mode under pulsed magnetization reversal. Numerical simulation and experimental results are compared.

The hot-deformed (HD) Nd-Fe-B magnets show heterogeneous microstructure composed of coarse and fine grain regions. It is significant to fully understand the influence of this complex microstructure on the magnetization reversal process which can give the guidance for the enhancement of the magnetic properties. In this paper, the heterogeneous microstructure of the (HD) Nd-Fe-B magnets were characterized from the morphology, size, macro-texture and micro-structure. In addition, the magnetization reversal process of the HD Nd-Fe-B magnets was systematically analyzed by magnetic measurement, in-situ domain evolution observation and micromagnetic simulation. The results indicate that the HD Nd-Fe-B magnets mainly consist of fine grain regions (FGRs) and coarse grain regions (CGRs). The FGRs show plate-like grains with fine grain size and strong c-axis texture, while the CGRs show equiaxial grains with large grain size and weak c-axis texture. In particular, it is worth noting that the texture in homogeneity exists not only between FGRs and CGRs, but also inside both the FGRs and CGRs. The dominant coercivity mechanism of the HD Nd-Fe-B magnets is domain wall pinning. Also, the experimental analysis shows that the reverse domain is formed and expanded in the CGRs at low reverse applied field, while the reverse domain occurs in the FGRs at higher reverse applied field. The micromagnetic simulation results also confirm the above magnetization reversal process. In addition, micromagnetic simulation results also show that the orientation of the grains also affects the pinning strength, besides the grain size.

A Ga-doped Nd-Fe-B sintered magnet has attracted significant attention as a heavy-rare-earth-free high-performance magnet. We have studied the temperature dependent magnetization reversal process of a Ga-doped Nd-Fe-B sintered magnet based on the first-order reversal curve (FORC) analysis. The FORC diagram pattern of the Ga-doped Nd-Fe-B sintered magnet changes from single spot in the high field region at room temperature to double spots in the low and high field regions at 200 °C, indicating that the dominant magnetization reversal process changes from single domain type to multidomain type. The single domain magnetization reversal at room temperature is well confirmed by using the soft X-ray magnetic circular dichroism microscopy observation. This change in the magnetization reversal process is well discussed by the temperature dependent local demagnetization field and the saturation field of multidomain state. Moreover, we have demonstrated the quantitative analysis of the FORC diagram pattern, which makes a deeper understanding of the magnetization reversal process of the Ga-doped Nd-Fe-B sintered magnet.

An amorphous GdFeCo film has a spin reorientation transition (SRT) with the temperature varying from 230 K to 300 K. Its magnetization reversal processes have been characterized by the hysteresis loops and first-order reversal curve (FORC) in the vicinity of the SRT temperature. Along with the SRT from out-of-plane to in-plane, the total irreversible components decrease with increasing temperature from 84% (250 K) to 13% (300 K) and the reversal process gradually changes from the pinning-type dominated reversal (250 K) to the nucleation type reversal (270 K), and then to the uniform rotation (300 K). The identification of the magnetization reversal process nearby SRT is important to understand the magnetic properties in the magneto-optical recording materials GdFeCo.

The heterogeneous ferromagnetic–superconducting layered heterostructures V/Fe0.7V0.3/V/Fe0.7V0.3/Nb and Nb/Ni0.65(0.81)Cu0.35(0.19), which contain magnetic clusters and ferromagnetic domains, are studied. The magnetic and superconducting properties of the structures depend on the magnetic-layer thickness, the magnetic field, and the time elapsed from structure preparation. We detected the interaction of clusters with a domain structure, diamagnetism and magnetization reversal of the magnetic layer during the superconducting transition in a ferromagnetic–superconducting heterostructure, and a superconducting transition in the magnetic layer. The magnetic and resistive properties of the heterostructures changed in several weeks and months.

Rapidly increasing demand for high-energy permanent magnets and volatility of the rear-earth market encourage a search of hard magnetic materials that can compete with those based on the Nd2Fe14B phase. Sm-Fe compounds with the ThMn12-type crystal structure are considered as promising candidates for it. However, their synthesis and achievement of theoretically predicted magnetic properties are still challenging tasks that have not been solved yet. This paper addresses this problem. Its aim was to synthesize and to study magnetic properties of the (Sm0.9Zr0.1)Fe11Ti compound with ThMn12-type structure. Initially amorphous alloy was obtained by melt spinning and its subsequent heat treatments were performed. Structural and phase transformations of the (Sm0.9Zr0.1)Fe11Ti alloy with annealing temperatures were studied along with magnetic properties. For the optimally annealed alloy features of magnetization reversal were discussed and temperature dependences of coercivity and maximum energy product were obtained.

The paper presents the proportions of the reversible and the irreversible magnetization processes along DC hysteresis loops of selected soft magnetic composite materials (Somaloy 700, also mixed with Vitrovac 6155 and Fe-phenolformaldehyde resin composites), obtained from the differential and the reversible permeability measurements. The magnetization reversal was described along minor hysteresis loops with different maximum inductions. The influence of ferromagnetic filler content, particle size distribution and ferromagnetic component type (selected) on the magnetization processes proportions was analysed, as well as the relations between these proportions and magnetic properties (coercive field, total energy losses and maximum permeability) were found.

In the present study, we present new experimental and calculated results of Co nanowires synthesized by the solvothermal method. The coercivity of 8.7 kOe and the energy product of 31.4 MGOe were obtained for wires of average diameters of 20 nm and average lengths of 200 nm. The experimental and numerical results of nanowires were discussed. Micromagnetic simulations were conducted to study the dependence of the magnetic properties on the nanowire aspect ratios, diameters, and various magneto-crystalline easy axis deviation angles from the long axis of Co nanowires. The calculation with a magneto-crystalline easy axis deviations from long axis show a better accordance with experimental results. The state graphs for reversal modes versus the magneto-crystalline easy axis deviation angles in Co nanowires were presented.

A theoretical approach to the consistent full quantum description of the ultrafast population transfer and magnetization reversal in superconducting meta-atoms induced by picosecond unipolar pulses of a magnetic field is developed. A promising scheme based on the regime of stimulated Raman Λ-type transitions between qubit states via upper-lying levels is suggested in order to provide ultrafast quantum operations on the picosecond time scale. The experimental realization of a circuit-on-chip for the discussed ultrafast control is presented.

Magnetization reversal and magnetic exchange coupling of (Co/Ni)×N/Ru/(Co/Pt)×12 were investigated as a function of the temperature. The number of repeats N of the soft multilayer (Co/Ni) was varied from 4 to 8 bilayers while the number of repeats of the hard bilayers (Co/Pt) was fixed to 12. Two steps hysteresis loops were observed for coupled structure with only 4 repeats of (Co/Ni) in a wide range of temperature (25–300 K). From the shift of the minor hysteresis loop, the antiferromagnetic exchange coupling Hex was measured and then the interlayer exchange coupling Jex was calculated. A non-monotonous dependence of Jex with temperature was observed for N = 4 with a maximum Jex of 0.13 erg/cm2 at 150 K. The annealing process performed on the same structure confirms the unusual behavior of interlayer exchange coupling Jex. As the repetition number N increases to 8 bilayers the two steps hysteresis loops disappeared in the investigated temperature range, however a small kink appeared in the range of 125 and 225 K for the case of 6 bilayers. From the analysis of the coupled and uncoupled structures, it seems that the dipolar energy overcomes the antiferromagnetic coupling for thicker (Co/Ni) multilayer.

Grain boundary modification induced giant coercivity enhancement from 945 kA/m to 1904 kA/m was achieved in Sm25Co48Fe20Cu5Zr2 magnets by doping 0.4 wt% CuO. Different magnetization reversal behaviors were clearly observed between un-doped and doped magnets. Compared with un-doped magnets, Cu enrichment along grain boundary promoting regular cellular structure was obviously found in doped magnet. The in-situ Kerr observation indicated that complete cellular structure could strengthen the pinning field of grain boundary regions and the propagations of magnetization reversals into interiors of grains were restrained by the modified grain boundaries, which resulted in the remarkable coercivity increment.

We present a model of hard/soft magnetic bilayer for the Monte Carlo investigation under the external magnetic field. The influence of the exchange interaction constants of soft magnetic layer Jsoft on the magnetic bilayer magnetization reversal processes is explored for the first time. Behavior of the magnetic bilayer under the external magnetic field is shown to agree with theoretical predictions well enough.

We have investigated the magnetic properties of ferromagnetic semiconductor GaMnAsP films with two different thicknesses. Temperature scans of the resistance revealed that the Curie temperature was higher in the 50-nm GaMnAsP layer than in the 16-nm layer, and was increased in both layers after annealing. The Hall effect was measured during the magnetization reversal process to identify the anisotropy of the films. The hysteresis observed from the as-grown samples in anomalous Hall resistance measurements implied the presence of out-of-plane magnetic anisotropy in both samples. The out-of-plane magnetic anisotropy in both samples became much stronger after thermal annealing. Quantitative values of the magnetic anisotropy of the GaMnAsP films were obtained from angular dependent Hall effect measurements. By constructing magnetic anisotropy energy diagrams for the films, we clearly show the change of magnetic anisotropy depending on the film thickness and thermal annealing in GaMnAsP films.

We studied the magnetoresistance effects in Co/Cu/Ni spin-valves with magnetic fields along different in-plane directions. When the magnetic easy axis directions of Co and Ni layers are parallel, only typical positive magnetoresistance effects were discovered. Interestingly, a magnetoresistance sign inverse was discovered in the spin-valve with different magnetic easy axis directions between Co and Ni layers. This anomalous behavior may be related to the multi-step magnetization reversal processes in these materials.