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Nontrivial chiral spin textures with nanometric sizes and novel characteristics (e.g., magnetic skyrmions) are promising for encoding information bits in future energy‐efficient and high‐density spintronic devices. Because of antiferromagnetic exchange coupling, skyrmions in ferrimagnetic materials exhibit many advantages in terms of size and efficient manipulation, which allow them to overcome the limitations of ferromagnetic skyrmions. Despite recent progress, ferrimagnetic skyrmions have been observed only in few films in the presence of external fields, while those in ferrimagnetic bulks remain elusive. This study reports on spontaneously generated zero‐field ground‐state magnetic skyrmions and their subsequent transformation into traditional magnetic bubbles via intermediate states of (bi‐)target bubbles during a magnetic anisotropy change in the rare‐earth ferrimagnetic crystal DyFe11Ti. Spontaneous reversible topological transformation driven by a temperature‐induced spin reorientation transition is directly distinguished using Lorentz transmission electron microscopy. The spontaneous generation of magnetic skyrmions and successive topological transformations in ferrimagnetic DyFe11Ti are expected to advance the design of topological spin textures with versatile properties and potential applications in rare‐earth magnets. [ABSTRACT FROM AUTHOR]

Z-type hexagonal ferrites have recently received attention for their room-temperature magnetoelectric (ME), which is activated when the temperature at which the transverse-conical spin-state transitions to a ferrimagnetic state is increased. The changes in the magnetic domain structure at the transition have been well-documented; however, they are still not understood in detail. In the present study, Lorentz transmission electron microscopy (TEM) analysis combined with an in situ heating experiment was conducted to demonstrate the shift in magnetic domain structure during the transition from the transverse-conical spin arrangement to a ferrimagnetic spin order. The dynamics of the magnetic domain structure changes with the increasing temperature were acquired in real-time. At 490 K, the magnetization transition from the transverse-conical spin state to the ferromagnetic state was demonstrated. Cross-tie domain walls formed during the magnetic transition process. The increased effect of the demagnetizing field applied to the 180° magnetic domains was caused by a lower magnetocrystalline anisotropy (MCA) at the easy axis of magnetization. [ABSTRACT FROM AUTHOR]

A Z1-type Fe 3 Pd alloy with negative enthalpy of formation at ambient pressure has been discovered recently, however, its physical properties under high pressures remain unclear. In this work, the effect of pressure on the magnetic, electronic, lattice dynamic, mechanical and thermal properties of the Z1-Fe 3 Pd are investigated thoroughly by the first-principles methods. Under high pressures, the Z1-Fe 3 Pd are energetically favorable compared to other types Fe 3 Pd structures. A pressure-induced magnetic phase transition from ferromagnetic (FM) to ferrimagnetic (FIM) state are found, and the FM and FIM states are dynamically and mechanically stable under high pressures. The electronic density of states for both the FM and FIM states are analyzed to understand their magnetism. These two magnetic configurations are ductile, but their elastic properties and anisotropy are quite different. Additionally, the FM and FIM states have high uniaxial magnetocrystalline anisotropy, the FM state is a semi-hard magnet, and the FIM state undergoes a transition from hard magnet to semi-hard magnet with pressure. Finally, the volume and linear thermal expansion coefficients under high pressure are calculated, and the anisotropy of thermal expansion is also discussed in detail. • A stable Fe 3 Pd structure under high pressure is discovered for the first time. • The pressure-induced magnetic phase transition from ferromagnetic to ferrimagnetic state is determined. • The structural stability is verified by formation enthalpy, phonon and elastic. • Elasticity, thermal expansion and their anisotropies are investigated. • Ferrimagnetic state transforms from a hard magnet to a semi-hard magnet under high pressure. [ABSTRACT FROM AUTHOR]

The electromagnetic (EM) properties of shielded gyromagnetic spheres are characterized with the aid of an electrodynamic model formulated for the transverse electric (TE) modes of an isotropic sphere, in a similar way as dielectric resonators are commonly analyzed. Broadband characteristics of geometric and energy filling factors are presented. A new measure of the magnetic loss tangent is introduced which is positive despite the intrinsic permeability of the gyromagnetic medium being negative, where existing definitions yield a non-physical negative value. The sample size dependence of those quantities is also assessed. The conclusions from the analysis are applied to investigate and de-embed ferromagnetic linewidth errors which can occur in broadband measurements of magnetic garnet spheres. Magnetic anisotropy fields and the gyromagnetic $g$ -factor are also estimated from the measurement data. Experiments were performed in a two-port subwavelength cavity, covering a frequency range of up to 28 GHz. Additionally, two-port rectangular resonant cavity linewidth measurements at a few modes have been conducted. Good agreement between the two methods is found if the systematic error is accounted for. [ABSTRACT FROM AUTHOR]

We report a study on the interfacial antiferromagnetic coupling between ferrimagnetic TbIG/YIG thin films. TbIG/YIG bilayers are grown on YAG (110) substrates. The crystal structure and magnetic properties of the films are characterized. The temperature and directional dependences of the antiferromagnetic coupling effect are observed at low temperatures. This work enriches the magnetic research of ferrimagnetic oxide films with complex structures, providing new ideas for the design of antiferromagnetically coupled spintronics devices. [ABSTRACT FROM AUTHOR]

Implementation of skyrmion based energy efficient and high-density data storage devices requires aggressive scaling of skyrmion size. Ferrimagnetic materials are considered to be a suitable platform for this purpose due to their low saturation magnetization (i.e. smaller stray field). However, this method of lowering the saturation magnetization and scaling the lateral size of skyrmions is only applicable where the skyrmions have a smaller lateral dimension compared to the hosting film. Here, we show by performing rigorous micromagnetic simulation that the size of skyrmions, which have lateral dimension comparable to their hosting nanodot can be scaled by increasing saturation magnetization. Also, when the lateral dimension of nanodot is reduced and thereby the skyrmion confined in it is downscaled, there remains a challenge in forming a stable skyrmion with experimentally observed Dzyaloshinskii–Moriya interaction (DMI) values since this interaction has to facilitate higher canting per spin to complete a 360° rotation along the diameter. In our study, we found that skyrmions can be formed in 20 nm lateral dimension nanodots with high saturation magnetization (1.30–1.70 MA/m) and DMI values (~ 3 mJ/m2) that have been reported to date. This result could stimulate experiments on implementation of highly dense skyrmion devices. Additionally, using this, we show that voltage controlled magnetic anisotropy based switching mediated by an intermediate skyrmion state can be achieved in the soft layer of a ferromagnetic p-MTJ of lateral dimensions 20 nm with sub 1 fJ/bit energy in the presence of room temperature thermal noise with reasonable DMI ~ 3 mJ/m2. [ABSTRACT FROM AUTHOR]

Crystal structure, magnetostriction, magnetic and magnetothermal properties have been studied for novel non-stoichiometric ErFe 2 Mn x (0 ≤ x ≤ 0.6) compounds. It has been found that for х ≤ 0.4 the compounds crystallize with MgCu 2 -type structure. Curie temperature and magnetic moment values decrease with manganese alloying. Molecular field coefficients have been calculated within ferrimagnetic two-sublattice molecular field model. Magnetic and heat capacity measurements have been used to calculate magnetocaloric effect in a wide temperature range. It has been demonstrated that increasing the Mn content in ErFe 2 Mn x leads to a significant increase (up to 39 %) of anisotropic magnetostriction value at 77 K in magnetic field of 18 kOe. At the same time, the value of effective magnetocrystalline anisotropy decreases. Thus, manganese alloying opens new way for tuning magnetocrystalline anisotropy and magnetostriction in Laves phase compounds. [Display omitted] • single phase non-stoichiometric ErFe 2 Mn х compounds are formed up to Mn concentration x = 0.4. • ErFe 2 Mn х compounds with x ≤ 0.2 have the compensation temperatures at М (Т) curves. • Curie temperature and magnetic moment values decrease with manganese alloying. • The value of anisotropic magnetostriction significant increase with increasing the Mn content. • The value of effective magnetocrystalline anisotropy decreases with increasing the Mn content. [ABSTRACT FROM AUTHOR]

The band alignment, intrinsic ferromagnetism, Dzyaloshinskii-Moriya interaction, magnetic anisotropy and critical temperature (T C) of a GdI 2 /GeC van der Waals (vdW) heterostructure were systematically investigated by first-principles calculations and Monte Carlo simulations. The proposed GdI 2 /GeC vdW heterostructure is a bipolar magnetic semiconductor with Type-I band alignment, large in-plane magnetic anisotropy energy (MAE) of − 0.912 mJ/m2 and high critical temperature of 466 K. In addition, under biaxial strains, the heterostructure transformed from semiconductor into metal, while the easy magnetization axis maintained in-plane and T C increased. The results indicated that the GdI 2 /GeC vdW heterostructure presented large MAE and high T C , having potential applications in spintronic devices. [Display omitted] ● The heterostructures is a bipolar magnetic semiconductor. ● The heterostructures with large in-plane magnetic anisotropy. ● The heterostructures with high critical temperature 466 K. [ABSTRACT FROM AUTHOR]

Co(Fe 1 -x Cr x) 2 O 4 (x = 0.02, 0.10, 0.15, 0.30, 0.50) samples are synthesized by the sol-gel method. The XRD patterns and subsequent Rietveld refinement provided structural analysis and confirmation of the samples' single-phase formation. XPS measurement reveals the existence of the elements Co, Cr and Fe in 2+ and 3+ oxidation states. The saturation magnetization (M s), coercivity (H c) and magnetocrystalline anisotropy (K 1) are observed to decline to as low as 10 emu/g, 35 Oe and 0.50 (106 erg/cm3) following Cr substitution, which indicated that the samples transform to a soft magnetic material. Cr substitution also lowers the ferrimagnetic (FiM) to paramagnetic (PM) transition temperature, T c , from 752 K for x = 0.02 to 307 K for x = 0.50. With Cr replacement, the dielectric constant and dielectric loss values decrease, indicating it to be a potential contender for high frequency applications. The dielectric constant for x = 0.30 and x = 0.50 samples rises sharply around 1 MHz owing to the LC resonance effect between the samples and the measurement leads. The ac conductivity plots are found to be in conformity with Jonscher's single power law, and the conduction process is revealed to be attributable to the small polaron hopping mechanism. • Cr substituted Cobalt ferrites has been synthesized in single phase form by sol-gel method. • Co, Cr and Fe exists only in 2+ and 3+ oxidation state. • Cr occupies only the octahedral sites. • Saturation magnetization, Coercivity and magnetocrystalline anisotropy are observed to decline following Cr substitution. • Dielectric constant and dielectric loss decreases with Cr substitution. [ABSTRACT FROM AUTHOR]

• The mechanical alloying reduced the sintering temperature to stabilize orthorhombic phase. • The site occupancy of Fe and Ga ions controlled ferrimagnetism, soft and hard magnetic phases. • The low temperature magnetic peak appeared due to magnetic frustration and anisotropy. • The extra moment with reference to spin value suggested contribution for orbital moment. • The ferrimagnetism and spin-phonon coupling indicated multiferroelectric nature in the system. A combined technique of mechanical alloying and heat treatment has been used to prepare the polycrystalline samples of Fe 2−x Ga x O 3 (x = 0.6–1.2) system in orthorhombic phase. It has been possible to reduce the sintering temperature by ~350 °C for stabilizing the orthorhombic phase in comparison to the temperature reported in literature. The Rietveld refinement of X-ray diffraction patterns indicated the distribution of Ga and Fe atoms in the Ga1, Ga2, Fe1 and Fe2 sites of the lattice structure. A linear variation of the lattice parameters with Ga/Fe content showed application of Vegard's law. The temperature-dependent magnetization measurements confirmed ferrimagnetic order of Fe spin moments. The ferrimagnetic transition temperature (T C) has decreased from 320 K to 100 K with the increase of Ga content in the range of x = 0.6–1.2. Temperature-dependent Raman spectroscopy data ruled out any structural phase transition at T C , but an anomalous behaviour of the position and width of the peaks of Raman active phonon modes near to T C confirmed a strong spin–phonon coupling in the material. The spin–phonon coupling strength (η) for the A9 mode has been found around 1.64 cm−1 for x = 1 and 3.34 cm−1 for x = 0.8, and η for the A21 mode has been found around 2.12 cm−1 for x = 1 and 3.28 cm−1 for x = 0.8. The spin-phonon coupling strength has been diluted in the samples with higher content of Ga. The experimental results indicated that the variation of Ga/Fe content and its distribution in lattice sites determine the ferrimagnetic properties, magnetic anisotropy and spin-phonon coupling in Fe 2−x Ga x O 3 system. The results are expected to be useful for understanding the spin-phonon coupling in multiferroic-magnetoelectric materials with magnetic and electric transitions near to room temperature. [ABSTRACT FROM AUTHOR]