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• Gd-content gradients influence PMA in both "+δ" and "−δ" samples. • "+δ" has lower H C due to closer T comp , suggesting different Gd-content. • Reversal of AHE loop near T comp indicates sublattice dominance shift. • Decrease in H SF suggests weakened exchange interaction near T comp. • Strong ΔR XY at ± 4 kOe and ± 30 kOe for "−δ" indicates enhanced PMA. Ferrimagnetic rare-earth (RE) – transition-metal (TM) alloys are considered small ferromagnets with antiferromagnetic exchange in sublattices, which makes them a preferable choice for future ultrafast memory-related applications. Here, we explore the magnetic properties of two GdFeCo thin films with tailored vertical composition gradients, achieved by gradually varying Gd concentration across the film thickness. The temperature-dependent magnetic behavior of these films is investigated using anomalous Hall effect (AHE) measurements and SQUID magnetometry. Both films exhibit perpendicular magnetic anisotropy with distinct coercivities, indicating variations in their magnetic properties. The films show RE-dominant behavior at 300 K. Moreover, for the positive composition gradient (+δ) film, the compensation temperature is around 350 K, while the film with a negative gradient (−δ) exhibits a compensation temperature above 400 K. Furthermore, the spin-flop behavior and AHE sign reversal provide insights into the sublattice dominance and exchange interactions within the films. The magnitude of ΔR XY (the difference in AHE resistance at different magnetic fields) is shown to be sensitive to the composition gradient, indicating stronger perpendicular magnetic anisotropy for the "−δ" sample. This study demonstrates the potential of composition engineering to tailor the magnetic characteristics of ferrimagnetic materials for specific spintronics applications. [ABSTRACT FROM AUTHOR]

The magnetic response of an identical magnetic nanoparticles (MNP) system to a rotating external field (RMF) is studied via Monte Carlo simulations. The field of amplitude H 0 and frequency ω , was applied in the y − z plane rotating clockwise. The energy was modeled by the Stoner–Wohlfarth scheme for fixed or random orientations of the anisotropy, and is in contact with a thermal bath at a temperature T. Interparticle dipolar interactions were also considered. In the non-interacting system and for low temperature, hysteresis is observed in the z magnetization component M z for both orientations of the anisotropy axis and only in the y component (M y) for the random case. Furthermore, the loop areas were estimated, and increased with ω for all orientations and ( M y , M z ) components. At higher temperatures the superparamagnetic state is observed, so both the blocking temperatures T B and loop areas were estimated. The values of T B were close from the room temperature T R = 300 K for all components, and the areas decreased with T but they are practically not zero at T B. When dipolar interactions are included a new scenario is revealed. In the low temperature regime, the blocked state is present for both M y and M z for all anisotropy orientations, and extends beyond the interval of amplitudes H 0 estimated theoretically for the model without interactions and fixed anisotropy. The loops are displaced with respect to the origin of the magnetization-external field plane. When the temperature is raised, the blocked state extends for a larger range than the model without interactions, and the loop displacement decreases with T. These behaviors could be explained by observing that the average dipolar field per particle produces an effective field – the sum of both dipolar and external field – that is asymmetric with respect to the zero field line at low temperatures, becomes half-wave symmetric at higher temperatures, so the the centered character of the loops is restored. In addition, the loop areas show a peak for all orientations of the anisotropy axes in an intermediate range of temperatures. This result can be associated with a dominance of the anisotropy induced by the dipolar field. Finally, by comparing the areas of the loops of the models with and without interactions, it was found that the non-interacting model have larger areas at low temperatures that vanish near the room temperature, unlike the areas of the model with interactions due to the extension of the blocked state. [ABSTRACT FROM AUTHOR]

Highlights • Magnetization, Cotton Mouton, and specific heat results obtained on DyIG single crystals are reported. • The first-order nature of the spin reorientation phase transition at T SR = 15 K is confirmed. • This ferrimagnet exhibits low temperature anomaly near the Belov point T B = 42 K. • The data are analyzed taking into consideration previous reports about magnetodielectric effect at T SR and Schottky anomaly around T B. Abstract Measurements of magnetization and Cotton Mouton effect (CM) under external magnetic field (H ex) combined with specific heat experiments at H ex = 0, were performed on dysprosium iron garnet Dy 3 Fe 5 O 12 (or DyIG) single crystals. The low-temperature dependences of some magnetic, magneto-optical and thermodynamic quantities, such as spontaneous magnetization, both magnetic and CM susceptibilities and the excess specific heat due to the contribution of the Dy3+ ions only, give rise to the appearance of two types of anomalies. The first one which is related to the 'low temperature paraprocess' effect, occurs in the region of the 'Belov point' T B predicted at 42 K. Whereas the second one, which is due to the previous first-order spin reorientation phase transition, takes place at T SR = 15 K. The easy axis of magnetization defined by the resultant iron sublattice magnetization vector M Fe , which remains along the 〈1 1 1〉 direction above T SR , changes spontaneously below T SR and becomes aligned along the low symmetry angular 〈u u w〉 phase. The results are analyzed taking into account those reported earlier, such as the negative magnetodielectric property for H ex < 10 kOe and the Schottky effect which are related to the anomalies observed respectively in the temperature dependences of the dielectric constant at T SR and the excess specific heat near T B. [ABSTRACT FROM AUTHOR]

Highlights • Effect of volume change on anisotropy. • Spin reorientation transition. • High volume stability of the magnetic properties. • Moderate decrease of the Curie temperature with increasing pressure. Abstract The magnetic properties of HoCo 12 B 6 ferrimagnetic compound are investigated versus the magnetic field, temperature and pressure. The magnetic phase diagram exhibits three remarkable temperatures: the ordering temperature T C , the spin reorientation temperature T SR and the compensation temperature T COMP at 147 K, 76 K and 47 K respectively. In HoCo 12 B 6 intermetallic system the spontaneous magnetization resulting from the antiparallel coupling of the magnetic moments of Ho and Co sublattices is pressure insensitive at lowest temperatures whereas it decreases with pressure at temperature range above T SR. The mean Co magnetic moment is small (<0.5 µ B) in the studied compound and exhibits a weak pressure dependence. In addition, significant pressure effects have been observed on both the spin reorientation transition and the Curie temperatures. A value of dT C /dp = −3.5 ± 0.4 K GPa−1 is dominated by the Co sublattice contribution. The spin reorientation transition temperature is also found to decrease versus pressure dT SR /dp = −4.2 ± 0.4 K GPa−1. The compensation temperature where the Ho and Co sublattices have the same magnitude but opposite direction does not vary significantly with applied pressure in the investigated pressure range (up to 1 GPa). The results of pressure dependence of the magnetic properties are compared to earlier results on other R-Co-B borides. HoCo 12 B 6 compound confirmed the remarkably high volume stability of the magnetic properties of the RCo 12 B 6 compounds with the itinerant character of magnetism and low values of both the T C and magnetization. [ABSTRACT FROM AUTHOR]

Highlights • A new method is developed quantitative phase control in soft ferrimagnetic materials. • The method is based on thermomagnetometric analysis of the samples in magnetic field. • This method compared to X-ray diffraction analysis is more precise. • The method was successfully tested on the LiTi and LiZn ferrites. Abstract In this work, the method of quantitative ferrite phase control, which is based on thermomagnetometric analysis of the ferrite samples in magnetic field, was developed. The magneto-phase transitions in LiZn and LiTi ferrites with chemical formulas Li 0.5(1 x) Fe 2.50.5 x Zn x O 4 and Li 0.5(1+ x) Fe 2.51.5 x Ti x O 4 were studied, and their phase compositions were analyzed by both the developed method and X-ray diffraction analysis. It was shown that the thermomagnetometry method compared to X-ray diffraction analysis allows to examine more precisely the magnetic phases in synthesized ferrites with inhomogeneous phase composition. However, a complex analysis, using both X-ray and thermomagnetometry methods, will be the most optimal in case of the formation of non-magnetic and poor magnetic phases. [ABSTRACT FROM AUTHOR]

Data of a magnetic susceptibility of ferro-and the ferrimagnetic particles of many technogenic, natural, special media are especially demanded for the solution of various tasks connected with purposeful magnetic impact on these particles. One of productive approaches to definition of a magnetic susceptibility χ of these particles consists in receiving experimental data of a susceptibility of disperse samples 〈 χ 〉 with a disperse phase of these particles. The paper expounds and analyses the results of experiments on defining (by Faraday method in a magnetic field with intensity H = 90–730 kA / m ) the magnetic susceptibility 〈 χ 〉 of disperse samples (conglomerates) with a given volume ratio γ of magnetite particles ( γ = 0.0065–0.25). The corresponding families of concentration and field dependences are provided alongside with discussing the applicability of linear and exponential functions to describe these dependences. We consider the possibility of defining single particles susceptibility χ (with simultaneous obtaining field dependence of this susceptibility) by the commonly used relation χ = 〈 χ 〉 / γ both at relatively small (preferable for accuracy reasons) values γ – to γ = 0.02…0.025, as well as at increased values γ – up to γ = 0.25. The data χ are provided depending on H and correlating with known data at H < 90 kA / m ; they are obtained at small values γ when with almost double distance between the neighbouring particles (in comparison with their proper dimensions) the mutual adverse (to determine valid data χ )magnetic impact of particles is practically excluded. The article also gives the data χ received at increased values γ with almost halved distance between the surfaces of the neighbouring particles. It is specified that in the studied (post-extreme) area of H both variants of obtained field dependences χ are functionally identical within the accuracy of a constant, and close to an exponential dependence χ ∼ 1/ H 0.75 . With the account for the defined here value of constant-multiplier (0.8), it provides the grounds for obtaining valid data χ , employing the results of measuring 〈 χ 〉 for conglomerates with not obligatory small values of γ . It is demonstrated that being obtained by data χ, the calculated field dependence of the particle matter magnetic susceptibility χm (for the case when the particles are traditionally likened to balls with the characteristic for them demagnetising factor equalling 1/3) complies with the anticipated inverse function χm ∼ 1/H in the studied area H (where magnetization M expressed as M = χH reaches saturation M = Const). [ABSTRACT FROM AUTHOR]

In this paper, we study the magnetic properties of ferrimagnetic mixed spins with integer σ = 2 and half-integer S = 7 / 2 in a Blume–Capel model, using Monte Carlo simulations. The considered Hamiltonian includes the first nearest-neighbors and the exchange coupling interactions on the two sub-lattices. The effect of these coupling exchange interactions, in the presence of both the external magnetic field and the crystal field, are studied. The magnetizations and the corresponding susceptibilities are presented and discussed. Finally, we have interpreted the behaviors of the magnetic hysteresis of this model. [ABSTRACT FROM AUTHOR]

Within the effective-field theory (EFT), the compensation behaviors in molecular-based ferrimagnet A F e Ι Ι F e Ι Ι Ι ( C 2 O 4 ) 3 which is described by a mixed spin-2 ( F e Ι Ι ) and spin-5/2 ( F e Ι Ι Ι ) ferrimagnetic Ising model on a honeycomb lattice are studied. The Glauber-type stochastic dynamic is used to describe the time evolution of the system under an oscillating magnetic field. A magnetic field dependence of the compensation temperature and a temperature dependence of compensating magnetic field are calculated and both curves agree qualitatively with experimental data. In particular, a two-compensation-points phenomenon which has been reported in the experimental work is also observed in this compound. Dynamic phase boundaries containing the compensation points are calculated. The dynamic tricritical point and critical end point exist on the phase transition lines. Comparing with previous theoretical results obtained by the mean-field theory (MFT), the effective-field theory results show a reasonable improvement over the MFT results. [ABSTRACT FROM AUTHOR]

There are two methods of preparation of ferrimagnetic spinel. If, during the preparation, an external magnetic field as high as 300 Oë is applied upon cooling the material is named field cooled. If the applied field is about 1 Oë the material is zero field cooled. To explore the magnetic and thermodynamic properties of these materials we consider two-sublattice spin system, defined on the bcc lattice, with spin- s A operators S i A at the sublattice A site and spin- s B operators S i B at the sublattice B site, where s A > s B . The subtle point is the exchange between sublattice A and B spins, which is antiferromagnetic. Applying magnetic field along the sublattice A magnetization, during preparation of the material, one compensates the Zeeman splitting, due to the exchange, of sublattice B electrons. This effectively leads to a decrease of the s B spin. We consider a model with s B varying parameter which accounts for the applied, during the preparation, magnetic field. It is shown that the model agrees well with the observed magnetization–temperature curves of zero field cooled and non-zero field cooled (FC) spinel ferrimagnetic spinel and explains the anomalous temperature dependence of the specific heat. [ABSTRACT FROM AUTHOR]

The magnetic properties of spins -S and σ Ising model on the Bethe lattice have been investigated by using the Monte Carlo simulation. The thermal total magnetization and magnetization of spins S and σ with the different exchange interactions, different external magnetic field and different temperatures have been studied. The critical temperature and compensation temperature have been deduced. The magnetic hysteresis cycle of Ising ferrimagnetic system on the Bethe lattice has been deduced for different values of exchange interactions between the spins S and σ , for different values of crystal field and for different sizes. The magnetic coercive filed has been deduced. [ABSTRACT FROM AUTHOR]

Nonequilibrium phase transition properties of a mixed Ising ferrimagnetic model consisting of spin-1/2 and spin-3/2 on a square lattice under the existence of a time dependent oscillating magnetic field have been investigated by making use of Monte Carlo simulations with a single-spin flip Metropolis algorithm. A complete picture of dynamic phase boundary and magnetization profiles have been illustrated and the conditions of a dynamic compensation behavior have been discussed in detail. According to our simulation results, the considered system does not point out a dynamic compensation behavior, when it only includes the nearest-neighbor interaction, single-ion anisotropy and an oscillating magnetic field source. As the next-nearest-neighbor interaction between the spins-1/2 takes into account and exceeds a characteristic value which sensitively depends upon values of single-ion anisotropy and only of amplitude of external magnetic field, a dynamic compensation behavior occurs in the system. Finally, it is reported that it has not been found any evidence of dynamically first-order phase transition between dynamically ordered and disordered phases, which conflicts with the recently published molecular field investigation, for a wide range of selected system parameters. [ABSTRACT FROM AUTHOR]

• The mixed spin Ising model is generally used as a modeling tool to study ferrimagnetism. • Monte Carlo simulation to study the critical and the compensation behaviors of a cubic lattice considering a mixed spin- 3/2 and spin-1 Ising ferrimagnetic model. • The presence of crystal and external magnetic fields is not sufficient to generate the compensation phenomenon in a mixed spins. In this study, we perform Monte Carlo simulations to study the magnetic properties of a mixed Ising model on a cubic lattice where spins S i A = 1 and σ J B = 3/2 are located in sublattice A and B, respectively. The proposed Hamiltonian includes coupling to nearest-neighbors interactions, next-nearest-neighbors interactions, crystal fields D S and D σ and external magnetic field h. We perform exact ground-state calculations for our model. The obtained results show the behavior of the critical temperature with the presence of the compensation temperatures under a certain range of parameters. Particularly, we found that the existence of compensation temperatures depends on the strength of the coupling to the next nearest neighbors between the S i A spins and between the σ J B spins, and it appears in a certain range of values of the external magnetic and crystal field of different spins. [ABSTRACT FROM AUTHOR]

• Dynamic magnetic properties of the borophene nanoribbon are studied using Monte Carlo method. • Dynamic order parameter Q versus the different physical parameters under fixed temperature are studied. • Various Q profiles and abundant saturation values are observed caused by different physical parameters. • Multi-loop hysteresis and superparamagnetic behavior are obtained under certain parameters. In this work, we applied Monte Carlo simulation to investigate the dynamic magnetic behaviors of the ferrimagnetic mixed-spin (3/2, 5/2) Ising-type borophene nanoribbons with core-shell structure. The effects of the crystal field, exchange couplings and time-dependent oscillating magnetic field on the dynamic magnetic characteristics were discussed. In addition, the hysteresis behaviors of the system were also presented and the multiple-loop hysteresis phenomena were observed. [ABSTRACT FROM AUTHOR]

• Successful electrochemical growth of ferrimagnetic CoFe 2 O 4 nanocomposite in nanoporous alumina membranes. • The annealing at 500 °C and cooling under an applied magnetic field produce a partially hard ferrimagnetic nanocomposite with an internal magnetic field of 1.52 T. • Analytical analysis and HFSS simulation are two powerful tools for determining the geometrical parameters of the coplanar topology of the circulator. • A first prototype is fabricated in the clean room and the microwave measurements of the S parameters have highlighted a circulation phenomenon of 3 dB. This paper is about a self-biased coplanar circulator. The design approach is based on the use of magnetic composite substrates self-polarized made from ferrimagnetic nanowires. It consists of integrating and orienting cobalt ferrite (CoFe 2 O 4) nanocrystallites in porous alumina membrane using the magneto-electrodeposition technique. XRD, SEM and EDX analysis confirmed the formation of the spinel phase of cobalt ferrite with a good distribution of Co, Fe and O elements in the unit cell of CoFe 2 O 4 nanowires. The performed SQUID-VSM measurements have revealed that the nano-composite electrodeposited and cooled under a magnetic field of 0.6 T has the best magnetic properties, i.e. a large anisotropy field (H a), moderate coercive field (H c), and partial squareness ratio ( M r / M s ). This nano-composite has been selected as an interesting candidate for the fabrication of a miniaturized self-biased circulator. The study has started with the implementation of an analytical dimensioning process based on Bosma's theory. Based on interesting HFSS simulation results, a first prototype was fabricated in the clean room and characterized at high frequencies. The measurements of the S parameters have highlighted a circulation phenomenon of 3 dB. [ABSTRACT FROM AUTHOR]

Abstract: Monte Carlo simulation based on Metropolis algorithm has been used with a great success to analyze the dynamic phase transition properties of a single spherical core–shell nanoparticle system with a spin-3/2 core surrounded by a spin-1 shell layer with antiferromagnetic interface coupling under the influence of a time dependent oscillating magnetic filed. It has been found that the dynamic phase boundaries strongly depend on the Hamiltonian parameters such as for the high amplitude and period values of the external field, the phase transition temperature sharply changes whereas it tends slowly to alter as the reduced magnitude of interlayer parameter increases. Moreover, it is observed that the magnetization curves of the particle have been found to obey P-type, N-type and Q-type classification schemes under certain conditions. Much effort has also been paid to the influence of the particle size on the thermal and magnetic properties of the particle. Finally, a comparison of our observations with those of recently published study including dynamic treatments of a nanocubic core–shell system is represented and the findings indicate that there exists a qualitatively good agreement with some relatively distinct differences. [Copyright &y& Elsevier]

• The graphene-like quantum dots with mixed-spin (3/2, 5/2) have been investigated. • The magnetic and thermodynamic behaviors have been explored. • The turnover phenomenon has been found. • The triple-loop behavior has been observed. Based on the Monte Carlo simulation, we have investigated the magnetic and thermodynamic behaviors of the graphene-like quantum dots described by a ferrimagnetic mixed-spin (3/2, 5/2) Ising model. The curves of the magnetization, magnetic susceptibility, internal energy and the specific heat as a function of temperature have been given under various physical parameters. The interesting turnover phenomenon has been found owing to the competition between the crystal field and temperature. It is found that the value of the blocking temperature increases with decreasing the crystal field or increasing the exchange coupling and external magnetic field. We have also investigated the hysteresis loops and found the impossibility of the triple-loop hysteresis behavior for certain parameters. The area of the hysteresis loops can be improved by increasing the exchange coupling and decreasing the absolute values of the crystal field and temperature. [ABSTRACT FROM AUTHOR]

• A ferrimagnetic double-layer core–shell Ising graphene nanoisland was studied in an oscillating magnetic field. • The dynamic order parameter, the susceptibility and the internal energy were discussed by Monte Carlo simulation. • The phase diagrams as well as the multiple-loop hysteresis behaviors were exhibited. • The behaviors of the coercivity and remanence under the influence of various parameters were investigated. By using Monte Carlo simulations, we discuss the dynamic magnetic properties of a double-layer core–shell graphene nanoisland with mixed-spin (2, 5/2) configuration in an oscillating magnetic field. We investigate the influence of exchange couplings, oscillating magnetic field, and temperature on the dynamic magnetic and thermodynamic properties of the system. We obtain the various characteristic curves of the dynamic order parameter, susceptibility, and internal energy as well as hysteresis loops. To better understand the impact of these physical parameters on the phase transition of the system, the phase diagrams are depicted. It should be noticed that the system can exhibit multiple-loop hysteresis behaviors under certain conditions. Besides, we plot the coercivity and remanence of the system under the influence of various parameters. [ABSTRACT FROM AUTHOR]

• The path probability method is applied the mixed spin (1/2, 1) model. • Dynamic magnetic hysteresis loop (DMHL) features of the system are studied. • Effects of interactions parameters on the DMHL features are examined. • Behaviors of coercive fields and remanents magnetizations as the function of angular frequency are investigated. Dynamic magnetic hysteresis loops (DMHL) features of molecular-based magnetic materials and ferrimagnetic systems are investigated by a mixed spin (1/2, 1) model by means of the path probability method (PPM). The PPM contains two rate constants; hence the DMHL features have been studied by using the method with two rate constants. In particular, the effects of the repulsive (J < 0) and attractive (J > 0) bilinear nearest-neighbor pair interactions, temperature (T), crystal-field interaction (D), angular frequency (ω) of the oscillating magnetic field and especially the rate constant (k 2) , which corresponds to the wheel speed in the melt spinning technique (MST), on the DMHL are investigated. The shapes and areas of hysteresis loops are affective sensibility by these system parameters. We also investigate the magnetic coercive fields and remanents magnetizations as a function ω. We found that the most of our results are in a good agreement with some theoretical and experimental reported works. We also observe the novel and interesting DMHL behaviors for lower values of T , and higher values of ω , k 2 and D. [ABSTRACT FROM AUTHOR]

• Synthesized magnetoelectric core shell architecture based on cobalt ferrite and zinc oxide. • The core size varied and studied its influence on the properties like piezoelectric, magnetic and magnetoelectric coupling. • Achieved stronger strain mediated elastic magnetoelectric coupling in the artificially engineered core shell structure. • Enhancement of Magnetoelectric coupling coefficient value with increase in core particle size. Artificially engineered magnetoelectric materials, whose electrical properties can be manipulated by an external magnetic field and vice versa are a new class of materials and find extensive applications in the field of emerging technologies like sensors, electrically controlled spintronic, and microelectronics and memory storage devices. Composites, having ferromagnetic and ferroelectric components are commonly employed where coupling between magnetic and electric fields is relatively weak. It is known that the interface between the components plays a very crucial role for achieving a stronger magnetoelectric (ME) coupling in artificially engineered magnetoelectric materials if the composites are synthesized with a ferro/ferri magnetic core and a ferro/piezoelectric shell. Such core-shell architecture ensures strong interaction and enables better connectivity. In realizing this goal, we report a simple technique to fabricate a core-shell nanostructure consisting of a ferrimagnetic core of CoFe 2 O 4 and a piezoelectric shell of ZnO. The core size is varied and the elastic strain mediated magnetoelectric coupling mechanism through the interface of the core-shell nanostructure is examined. [ABSTRACT FROM AUTHOR]

• Minimum frequency of the BV spin wave was tracked for a wide range of field angles. • Data are compared with a recently developed theory. • Disagreement between data and the theory was found at low frequency. Using parametric excitation, we have studied the minimum frequency associated with the backward volume (BV) spin wave branch in a thin film of the ferrimagnetic material yttrium iron garnet (YIG) for the magnetic field lying in plane and parallel to the wave vector as well as for out-of-plane field angles. We find that there is a drastic change in the efficiency of parametric excitation between two different pumping frequency regimes. [ABSTRACT FROM AUTHOR]

• The granular nanotubes calcination of cobalt ferrite produces octahedrons. • Particles grow as octahedrons due to a minimization of the surface free-energy. • The heat treatment increases the sizes of the crystallites and particles. • The curves ZFC and FC are characterized by a peak and irreversibility temperatures. • Irreversibility temperature behavior is similar to superparamagnetic systems. • The magnetic domain structure is highly dependent on the applied magnetic field. We present an in-depth magnetic study of polycrystalline, microstain-free, magnetic, and thermally stable cobalt ferrite (CoFe 2 O 4) octahedrons with an edge dimension of 214 nm. Nanoparticles were synthesized from granular CoFe 2 O 4 nanotubes growing on bacterial nanocellulose and annealed at T = 1273 K. SEM, XRD, and VSM were used to investigate the morphology, structure and magnetic properties of the octahedral particles. The results indicate that heat treatment increases the sizes of the crystallites (2 times) and of the particles (4 times), compared with the starting material. The particles show a change of the magnetization saturation and magnetic anisotropy around 150 K compared with canonical ferrimagnetic materials, associated with a First Order Magnetization Process. The magnetization process as a function of temperature, cooling without (ZFC) and with (FC) different applied magnetic fields are explained by multi-domain theory. ZFC-FC curves show an irreversible branching temperature, which is highly sensitive to the applied magnetic field. In contrast, the temperature for the maximal magnetization value in the ZFC curves, change slightly with the external applied magnetic field, H. [ABSTRACT FROM AUTHOR]

• Single layered magnetic thin film including both ferromagnetic and antiferromagnetic couplings could be prepared. • Nanostructures and increased density of the internal interfaces within the film significantly enhance the exchange bias effect compared with the conventional thin film structures. • Low blocking temperature with the nanoscale antiferromagnet could be avoided by combining the conventional layer with the nanostructured layer. • Conventional limits of interfacial exchange bias effect in the thin film structure could be overcome by the formation of nanostructured internal interfaces. Phase mixture single layer film with 3-dimensional spatial distribution of internal interfaces between ferromagnetic and antiferromagnetic nanoclusters was achieved through the inhomogeneous distribution of oxygen atoms within the ferromagnetic transition metal thin film layer. In the present work, enhanced exchange bias properties of phase mixture single layer film including both exchange and super-exchange couplings within the body of the single layer were investigated under various conditions. The film exhibited same exchange bias field regardless of the layer thickness, which violates the known relationship of inverse proportionality between the exchange bias field and the thickness of the magnetic layer in the conventional ferromagnet/antiferromagnet bilayers systems. Furthermore, it was found that the exchange bias could be set in any direction with respect to the film surface, removing the restriction by the magnetic shape anisotropy of the thin film structure. Low blocking temperature of the phase mixture single layer film could also be overcome with an additional neighboring antiferromagnet layer. [ABSTRACT FROM AUTHOR]

• The magnetic properties of α-Fe 2 O 3 and Fe 3 O 4 cannot be control by electric field. • The α-Fe 2 O 3 /Fe 3 O 4 composite structure is obtained by vacuum annealing of the α-Fe 2 O 3. • The magnetic properties of α-Fe 2 O 3 /Fe 3 O 4 can be reversibly and non-volatilely modulated. • The electric control of magnetism is due to the mechanism of phase transition. The raw nano α-Fe 2 O 3 powders consisting of nanorods with 50–100 nm in length and 8–14 nm in width exhibit superparamagnetism. The vacuum annealing of the raw nano α-Fe 2 O 3 at 400 °C for 3 h leads to ferromagnetic-like behaviors at room temperature (RT), due to the appearance of ferrimagnetic Fe 3 O 4. The α-Fe 2 O 3 /Fe 3 O 4 composite structure has an antiferromagnetic α-Fe 2 O 3 layer and a ferrimagnetic Fe 3 O 4 layer contains a certain amount of Fe2+ and oxygen vacancies. In addition, nano α-Fe 2 O 3 annealed in H 2 at 300 °C for 3 h completely become Fe 3 O 4. Some magnetic properties of the α-Fe 2 O 3 /Fe 3 O 4 , such as magnetization, magnetic remanence (Mr), coercivity (Hc) and exchange bias (EB), can be modulated almost reversibly and non-volatilely by applied external RT electric field without loop current. However, for both the raw nano α-Fe 2 O 3 and the Fe 3 O 4 , these magnetic properties cannot be modulated by applied external RT electric field. The electric field control of magnetic properties for the α-Fe 2 O 3 /Fe 3 O 4 should be due to the mechanism of phase transition induced by migration and redistribution of oxygen vacancies within the interface of α-Fe 2 O 3 /Fe 3 O 4. [ABSTRACT FROM AUTHOR]