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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]

The Monte Carlo simulation has been used to investigate the magnetic properties of a mixed spin-1 (sublattice A) and spin-1/2 (sublattice B), where each sublattice has a rectangular structure and the whole lattice system forms a 2-D centered rectangular lattice. Five possible interactions are considered. Namely, two S–S interactions and two $\sigma $ – $\sigma $ interactions depend on crystal direction, and an antiferromagnetic interaction between the two sublattices is taken. Our results show that the critical temperature increases with increasing the variation of any exchange interactions. The existence of the compensation temperature depends on the balance between the S–S interactions along and $\sigma $ – $\sigma $ interactions along [01] directions. [ABSTRACT FROM AUTHOR]

In 3 d − 4 f intermetallic compounds, a Co substitution for Fe usually strengthens the exchange interactions due to a shift of the Fermi energy to a region of the 3 d band with higher density of states. Here, we study the influence of Co on the magnetism of ferrimagnetic DyFe 5 Al 7 using magnetization measurements in static (up to 14 T) and pulsed (up to 58 T) magnetic fields. We find that the homogeneity range of DyFe 5− x Co x Al 7 is limited to x ≤ 2.5 . The Co substitution for Fe produces a strong detrimental effect on the 3 d − 3 d intrasublattice exchange interactions, which leads to a pronounced decrease of the Curie temperature and of the 3 d − 4 f intersublattice exchange field. A reduction of the density of states at the Fermi level might occur due to a broadening of the 3 d band. A decrease of the rare-earth contribution to the magnetic anisotropy energy is also observed with increasing Co content. This is attributed to a competition between the Fe and Co contributions to the crystal electric field at the Dy site. [ABSTRACT FROM AUTHOR]

Tunability of structural and magnetic properties of Mn 3- x Co x Ga films is presented by Co substitution, where critical behavior emerges 0.37 ≤ x ≤ 0.56 exhibiting a transition from tetragonal hard ferrimagnetic with perpendicular magnetic anisotropy (PMA) to a cubic soft ferrimagnetic phase with in-plane magnetic anisotropy (IMA). In the critical regime, coexisting state of tetragonal and cubic phases possesses significantly low coercive field (H C = 1.9 kOe) with relatively low saturation magnetization (M S = 100~150 emu/cc) while maintaining the PMA. From first-principles calculations, moments of two Mn sites do not change upon Co substitution. However, moments of substituted Co almost vanish in tetragonal while giving around 1 μ B in cubic phase, which agrees with overall M S behaviors of the experimental results. These findings not only uncover the hidden magnetic state in Mn 3- x Co x Ga by altering the parallel and antiparallel coupling between Mn and Co, but also provide an additional degree of freedom for spintronic applications using Mn-based Heusler compounds. • Critical regime during the transition from hard ferrimagnetic tetragonal to soft ferrimagnetic cubic in Co-substituted Mn3Ga. • Dramatic reduction of the coercive field on remaining perpendicular magnetic anisotropy in the critical regime. • Compensation point near this critical regime due to a large reduction of the Co moments when substituted in Mn 3 Ga. [ABSTRACT FROM AUTHOR]

Anisotropy and competing exchange interactions have emerged as two central ingredients needed for centrosymmetric materials to exhibit topological spin textures. Fe 3 Sn 2 is thought to have these ingredients as well, as it has recently been discovered to host room temperature skyrmionic bubbles with an accompanying topological Hall effect. We present small-angle inelastic neutron scattering measurements that unambiguously show that Fe 3 Sn 2 is an isotropic ferromagnet below T C ≈ 660 K to at least 480 K—the lower temperature threshold of our experimental configuration. Fe 3 Sn 2 is known to have competing magnetic exchange interactions, correlated electron behavior, weak magnetocrystalline anisotropy, and lattice (spatial) anisotropy; all of these features are thought to play a role in stabilizing skyrmions in centrosymmetric systems. Our results reveal that at the elevated temperatures measured, there is an absence of significant magnetocrystalline anisotropy and that the system behaves as a nearly ideal isotropic exchange interaction ferromagnet, with a spin stiffness D (T = 480 K ) = 168 meV Å 2 , which extrapolates to a ground state spin stiffness D (T = 0 K ) = 231 meV Å 2 . [ABSTRACT FROM AUTHOR]