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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]

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]

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]

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]

• 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]

• 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 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]

• 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]