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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]

Anisotropy of magnetic susceptibility (AMS) and anisotropy of magnetic remanence (AARM and AIRM) are efficient and versatile techniques to indirectly determine rock fabrics. Yet, deciphering the source of a magnetic fabric remains a crucial and challenging step, notably in the presence of ferrimagnetic phases. Here we use X‐ray micro‐computed tomography to directly compare mineral shape‐preferred orientation and spatial distribution fabrics to AMS, AARM and AIRM fabrics from five hypabyssal trachyandesite samples. Magnetite grains in the trachyandesite are euhedral with a mean aspect ratio of 1.44 (0.24 s.d., long/short axis), and >50% of the magnetite grains occur in clusters, and they are therefore prone to interact magnetically. Amphibole grains are prolate with magnetite in breakdown rims. We identified three components of the petrofabric that influence the AMS of the analyzed samples: The magnetite and the amphibole shape fabrics and the magnetite distribution anisotropy. Depending on their relative strength, orientation and shape, these three components interfere either constructively or destructively to produce the AMS fabric. If the three components are coaxial, the result is a relatively strongly anisotropic AMS fabric (P' = 1.079). If shape fabrics and/or magnetite distribution anisotropy are non‐coaxial, the resulting AMS is weakly anisotropic (P' = 1.012). This study thus reports quantitative petrofabric data that show the effect of magnetite distribution anisotropy on magnetic fabrics in igneous rocks, which has so far only been predicted by experimental and theoretical models. Our results have first‐order implications for the interpretation of petrofabrics using magnetic methods. Key Points: Trachyandesite analyzed with X‐ray microtomography for comparison between magnetic fabrics and the components of the petrofabricMagnetite and amphibole shape fabrics and magnetite distribution constructively or destructively interfere to produce magnetic fabricsDistribution anisotropy significantly affects the anisotropy of magnetic susceptibility and anisotropy of remanent magnetization [ABSTRACT FROM AUTHOR]

The cobalt(II) in [Co(NCS)2(4‐methoxypyridine)2]n are linked by pairs of thiocyanate anions into linear chains. In contrast to a previous structure determination, two crystallographically independent cobalt(II) centers have been found to be present. In the antiferromagnetic state, below the critical temperature (Tc=3.94 K) and critical field (Hc=290 Oe), slow relaxations of the ferromagnetic chains are observed. They originate mainly from defects in the magnetic structure, which has been elucidated by micromagnetic Monte Carlo simulations and ac measurements using pristine and defect samples. The energy barriers of the relaxations are Δτ1=44.9(5) K and Δτ2=26.0(7) K for long and short spin chains, respectively. The spin excitation energy, measured by using frequency‐domain EPR spectroscopy, is 19.1 cm−1 and shifts 0.1 cm−1 due to the magnetic ordering. Ab initio calculations revealed easy‐axis anisotropy for both CoII centers, and also an exchange anisotropy Jxx/Jzz of 0.21. The XXZ anisotropic Heisenberg model (solved by using the density renormalization matrix group technique) was used to reconcile the specific heat, susceptibility, and EPR data. [ABSTRACT FROM AUTHOR]

Reactions of [Mn(H2dapsc)Cl2]⋅H2O (dapsc=2,6‐ diacetylpyridine bis(semicarbazone)) with K3[Fe(CN)6] and (PPh4)3[Fe(CN)6] lead to the formation of the chain polymeric complex {[Mn(H2dapsc)][Fe(CN)6][K(H2O)3.5]}n⋅1.5n H2O (1) and the discrete pentanuclear complex {[Mn(H2dapsc)]3[Fe(CN)6]2(H2O)2}⋅4 CH3OH⋅3.4 H2O (2), respectively. In the crystal structure of 1 the high‐spin [MnII(H2dapsc)]2+ cations and low‐spin hexacyanoferrate(III) anions are assembled into alternating heterometallic cyano‐bridged chains. The K+ ions are located between the chains and are coordinated by oxygen atoms of the H2dapsc ligand and water molecules. The magnetic structure of 1 is built from ferrimagnetic chains, which are antiferromagnetically coupled. The complex exhibits metamagnetism and frequency‐dependent ac magnetic susceptibility, indicating single‐chain magnetic behavior with a Mydosh‐parameter φ=0.12 and an effective energy barrier (Ueff/kB) of 36.0 K with τ0=2.34×10−11 s for the spin relaxation. Detailed theoretical analysis showed highly anisotropic intra‐chain spin coupling between [FeIII(CN)6]3− and [MnII(H2dapsc)]2+ units resulting from orbital degeneracy and unquenched orbital momentum of [FeIII(CN)6]3− complexes. The origin of the metamagnetic transition is discussed in terms of strong magnetic anisotropy and weak AF interchain spin coupling. [ABSTRACT FROM AUTHOR]

A step-by-step engineering approach offering a model for the characterization of magnetic composite materials is presented. The modelling of composite materials containing unbiased ferrites is a subject of great interest, due to extended range of applications, such as hyperthermia and microwave absorbers. Here, unbiased ferrites simplify the application structure, as they do not require a biasing field, while they can resonate at low microwave frequencies due to their innate magnetocrystalline anisotropy field. However, so far there has not been an explicit organized step-by-step engineering modelling approach. The homogenization approximation formula is used in conjunction with Landau-Lifshitz-Gilbert equation solution to systematically compute the complex effective permeability and compare it with published measurements, from an engineer's result-focused perspective. For further validation, simulations of these composite materials as periodic structures are carried out, which additionally provide useful insight on the electromagnetic field distributions within the composites and are often more accurate. The results of the proposed procedure show good agreement with the experimental ones, which validate it, while the relatively greater error appears for the imaginary parts. The EM field distributions suggest that better focusing around the nanoparticles is achieved when those are large enough to form magnetic domains. [ABSTRACT FROM AUTHOR]

A series of two types of stochastic magnetization jumps in K0.4[Cr(CN)6][Mn( R/ S)-pn]( R/ S)-pnH0.6 single crystals (pn = 1,2-diaminopropane) are reported. Large jumps appear on the demagnetization branch of the hysteresis loop at the critical value of the decreasing magnetic field. The correlation of the temperature dependence of jump magnetic field and the temperature dependence of magnetic anisotropy field indicates a contribution of magnetic anisotropy to nonlinear spin-soliton structure. Small magnetization jumps occur in both magnetization and demagnetization regimes. [ABSTRACT FROM AUTHOR]

Antiferromagnetic(AFM)/ferrimagnetic(FiM) Co0.3Fe0.7O/Co0.6Fe2.4 O4 core-shell nanoparticles (NPs) with a particle size of 6-18 nm are prepared by a one-pot thermal decomposition process according to the literature involving mixed Fe and Co oleate complexes. [ABSTRACT FROM AUTHOR]