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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]

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 magnetic structure of La 1- x Tb x Mn 2 Si 2 compounds with 0 ≤ x ≤ 1 has been studied by powder neutron diffraction and magnetization measurements on single-crystal samples. We demonstrate that at 4.2 K, with increasing the Tb concentration, a canted ferromagnetic structure of LaMn 2 Si 2 changes at x > 0.2 to a canted antiferromagnetic structure. The antiferromagnetic in-plane component of Mn moment decreases with increasing concentration x and vanishes at x > 0.5. TbMn 2 Si 2 is characterized by a collinear in-plane Mn ordering and ferrimagnetic structure, in which the Mn sublattice possesses the ferromagnetic interlayer alignment along the easy c -axis. Neutron diffraction study does not reveal a long-range magnetic order of Tb moments for the compounds with x ≤ 0.4. Our results show that for concentrations 0.2 < x ≤ 0.4, a competition of the interlayer Tb-Mn, Mn-Mn exchange interactions and strong uniaxial magnetic anisotropy leads to formation of a frustrated magnetic state of Tb ions, which prevents magnetic ordering in the Tb sublattice. [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]

Abstract: Large sized α-Li3Fe2(PO4)3 single crystals with high quality are successfully grown by a flux method. Magnetic behaviors of the grown crystals are investigated by means of magnetic susceptibility, magnetization, and heat capacity measurements along different directions. The results confirm that α-Li3Fe2(PO4)3 exhibits weak ferrimagnetic behaviors at low temperature, which are in good agreement with those reported previously. However magnetic anisotropy is confirmed for the first time, suggesting that the c-axis is the likely magnetic easy axis and the a-axis is the magnetic hard one. Two anomalies are clearly observed in magnetic susceptibility along the a-axis and heat capacity data at zero field, suggesting the appearance of two successive magnetic transitions at ~26 and ~22K in the system. [Copyright &y& Elsevier]