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The discovery of van der Waals (vdW) magnetic materials exhibiting non-trivial and tunable magnetic interactions can lead to exotic magnetic states that are not readily attainable with conventional materials. Such vdW magnets can provide a unique platform for studying new magnetic phenomena and realizing magnetization dynamics for energy-efficient and non-volatile spintronic memory and computing technologies. Here, the coexistence of ferromagnetic and antiferromagnetic orders in vdW magnet (Co_0.5Fe_0.5)_5-xGeTe₂ (CFGT) above room temperature, inducing an intrinsic exchange bias and canted perpendicular magnetism is discovered. Such non-trivial intrinsic magnetic order enables to realize energy-efficient, magnetic field-free, and deterministic spin-orbit torque (SOT) switching of CFGT in heterostructure with Pt. These experiments, in conjunction with density functional theory and Monte Carlo simulations, demonstrate the coexistence of non-trivial magnetic orders in CFGT, which enables field-free SOT magnetization dynamics in spintronic devices.

The nonstoichiometric Fe₂P-type FeMn_(1-x)V_x(P_0.5Si_0.5)_1-x alloys (x = 0, 0.01, 0.02, and 0.03) have been investigated as potential candidates for magnetic refrigeration near room temperature. The magnetic ordering temperature decreases with increasing FeV concentration x, which can be ascribed to decreased ferromagnetic coupling strength between the magnetic atoms. The strong magnetoelastic coupling in these alloys results in large values of the isothermal entropy change (ΔS_M); 15.7 J/(kg K), at 2 T magnetic field for the x = 0 alloy. ΔS_M decreases with increasing x. Results from Mössbauer spectroscopy reveal that the average hyperfine field (in the ferromagnetic state) and average center shift (in the paramagnetic state) have the same decreasing trend as ΔS_M. The thermal hysteresis (ΔT_hyst) of the magnetic phase transition decreases with increasing x, while the mechanical stability of the alloys improves due to the reduced lattice volume change across the magnetoelastic phase transition. The adiabatic temperature change ΔT_ad, which highly depends on ΔT_hyst, is 1.7 K at 1.9 T applied field for the x = 0.02 alloy.

Cationic redistribution in spinel ferrite systems greatly influences the magnetic ordering and theassociated phenomena. Here, the effect of the synthesis condition on the cationic redistributionand its correlation with the magnetic properties were explored in the Cu2+ substituted ZnFe2O4spinel ferrite. X-ray photoelectron spectroscopy and x-ray diffraction studies reveal that thevariation of sintering temperature redistributes the cations between tetrahedral and octahedralsublattices. Results from low field dc-magnetic susceptibility measurements show that thesusceptibility increases with decreasing sintering temperature of the sample. Furthermore, theac-susceptibility results suggest that the sample sintered at 1048 K (1148 K) exhibits spin-glassbehavior with a glass transition temperature of ∼49.2 K (47.1 K) and a cluster-glass behavior ata higher temperature of ∼317 K (330 K), characteristics that are absent in the sample sintered at1248 K. The sample annealed at 1048 K exhibits a magnetocaloric effect with a maximumisothermal entropy change of ∼1.21 J kg−1 K−1 at μ0H = 5 T.

LiFe₆Ge₄, with a theoretically predicted saturation magnetization of 1 T, a magnetocrystalline anisotropy energy of 1.78 MJ/m³ and a Curie temperature of 620 K was suggested to be a promising permanent magnet as an outcome of a data-mining search. Magnetic measurements of the synthesized sample are reported here. Unfortunately, experiments revealed a weak ferromagnetic behaviour with magnetization values much below that predicted by theory. This discrepancy is analyzed in detail, and is attributed to the trigonal crystal symmetry that was missed in the previous characterisation of the material. The correct crystal structure is R¯3 mH (space group 166) and it is found here to have an antiferromagnetic ground state, as opposed to a theoretically predicted ferromagnetic state of the previously reported monoclinic crystal structure. Theoretical calculations show that element substitution can stabilize a ferromagnetic state of the trigonal crystal structure, with high values of saturation magnetization and magnetocrystalline anisotropy. The best results are seen for the Al or Ga substitution for Ge of the LiFe₆ X₄ compound.

The magnetic properties of Fe_2−2xMn_2xP_1−xSi_x (0 ≤ x ≤ 0.5) compounds are studied by neutron diffraction, Mössbauer spectroscopy, and magnetometry. DC magnetization measurements indicate that compounds with 0.2 ≤ x ≤ 0.5 undergo a paramagnetic to ferromagnetic transition, with the Curie temperature increasing as x increases. In contrast, compounds with 0 < x ≤ 0.15 show unclear magnetic ordering in DC magnetization measurements, while AC magnetization measurements display frequency-dependent peaks, indicating glassy spin dynamics. For the x = 0.125 sample, AC magnetization measurements under applied DC fields suggest that the transition at 150 K corresponds to a complex antiferromagnetic (AFM) structure. Mössbauer spectroscopy reveals four distinct regions of hyperfine interactions for different x values, suggesting extreme sensitivity in the magnetic behaviour with Mn and Si substitutions. For 0 < x < 0.15, a drop in the magnetic hyperfine field supports the existence of a complex AFM structure. Neutron diffraction on the x = 0.1 sample confirms an incommensurate AFM structure with a propagation vector q_x = 0.2204(4), consistent with the Mössbauer and magnetization results.

Environmental magnetism, including the use of magnetic susceptibility (MS), has formed the backbone of analyzing past terrestrial climate dynamics recorded in loess deposits world-wide. However, the nature of MS signal response and frequency dependence (χ_FD) varies between loess sequences, which can limit the applicability of the approach. Here, we explore how measuring MS using multiple alternating-current field frequencies can transform our understanding of the past climate record in loess. We compare loess MS data measured at 15 different frequencies from diverse environments across the Northern Hemisphere, and provide high-resolution data for a late Quaternary loess-paleosol section in Tajikistan. Additionally, we study the magnetic mineral composition in selected Tajik loess samples using rock magnetic methods and Raman spectroscopy and assess the usefulness of calculating superparamagnetic nanoparticle (SP) size distributions from multi-frequency magnetic susceptibility. Our results demonstrate that using this approach to determine χ_FD has several advantages over widely used dual-frequency approaches: (a) Inclusion of a wider grain size range of magnetism-bearing SP particles in measuring χ_FD, allowing for a more complete analysis of the environmental drivers behind the MS signal; (b) Higher sensitivity of the χ_FD palaeoclimate proxy to climatic changes; and (c) Increased statistical meaningfulness of the χ_FD proxy by allowing quantification of uncertainty. Our approach is particularly beneficial for understanding sites characterized by low-susceptibility samples and potentially diverse processes of magnetic enhancement. However, we advocate its routine use even in more typical loess sequences due to its greater sensitivity to climatic changes and better understanding of inherent proxy uncertainties.

We report on the discovery of a boundary-induced body-centered tetragonal iron phase in thin films deposited on MgAl2⁢O4 (001) substrates. We present evidence for this phase using detailed x-ray analysis and ab initio density functional theory calculations. A lower magnetic moment and a rotation of the easy magnetization direction are observed, as compared with body-centered cubic iron. Our findings expand the range of known crystal and magnetic phases of iron, providing valuable insights for the development of heterostructure devices using ultrathin iron layers.

Due to their high potential energy storage, magnetite (Fe₃O₄) nanoparticles have become appealing as anode materials in lithium-ion batteries. However, the details of the lithiation process are still not completely understood. Here, we investigate chemical lithiation in 70 nm cubic-shaped magnetite nanoparticles with varying degrees of lithiation, x = 0, 0.5, 1, and 1.5. The induced changes in the structural and magnetic properties were investigated using X-ray techniques along with electron microscopy and magnetic measurements. The results indicate that a structural transformation from spinel to rock salt phase occurs above a critical limit for the lithium concentration (x_c), which is determined to be between 0.5< x_c ≤ 1 for Fe_3−δO₄. Diffraction and magnetization measurements clearly show the formation of the antiferromagnetic LiFeO₂ phase. Upon lithiation, magnetization measurements reveal an exchange bias in the hysteresis loops with an asymmetry, which can be attributed to the formation of mosaic-like LiFeO₂ subdomains. The combined characterization techniques enabled us to unambiguously identify the phases and their distributions involved in the lithiation process. Correlating magnetic and structural properties opens the path to increasing the understanding of the processes involved in a variety of nonmagnetic applications of magnetic materials.

The conditions whereby epitaxy is achieved are commonly believed to be mostly governed by misfit strain. We report on a systematic investigation of growth and interface structure of single crystalline tungsten thin films on two different metal oxide substrates, Al₂O₃ (11‾20) and MgO (001). We demonstrate that despite a significant mismatch, enhanced crystal quality is observed for tungsten grown on the sapphire substrates. This is promoted by stronger adhesion and chemical bonding with sapphire compared to magnesium oxide, along with the restructuring of the tungsten layers close to the interface. The latter is supported by ab initio calculations using density functional theory. Finally, we demonstrate the growth of magnetic heterostructures consisting of high-quality tungsten layers in combination with ferromagnetic CoFe layers, which are relevant for spintronic applications.

The search for energy-efficient and environmentally friendly cooling technologies is a key driver for the development of magnetic refrigeration based on the magnetocaloric effect (MCE). This phenomenon arises from the interplay between magnetic and lattice degrees of freedom that is strong in certain materials, leading to a change in temperature upon application or removal of a magnetic field. Here we explore in detail an emerging material, Mn1-xFexNiSi0.95Al0.05, with an exceptionally large isothermal entropy at room temperature. By combining experimental and theoretical methods we outline the microscopic mechanism behind the large MCE in this material. It is demonstrated that the competition between the Ni2In-type hexagonal phase and the TiNiSi-type orthorhombic phase, that coexist in this system, combined with the distinctly different magnetic properties of these phases, is a key parameter for the functionality of this material for magnetic cooling.