Magnetic phase transitions in the LiNi0.9 M 0.1PO4 (M = Mn, Co) single crystals

The LiNiPO4, LiNi0.9Mn0.1PO4, and LiNi0.9Co0.1PO4 single crystals are studied with heat capacity and neutron diffraction measurements over the temperature interval (10–30) K. Two peaks are observed on the temperature dependence of heat capacity for LiNiPO4, and LiNi0.9Co0.1PO4 samples. One peak indicates the first order phase transition from an antiferromagnetic commensurate (C) structure to an incommensurate (IC) one upon heating. According to neutron diffraction, in LiNiPO4 the IC ordering is described by the propagation vector k = 2π/b(0, 0.080, 0) at the Néel temperature T N = 20.8 K, and k = 2π/b(0, 0.098, 0) at T N = 20.2(1) K for LiNi0.9Co0.1PO4. A further increase in temperature leads to the second order phase transition to a paramagnetic state at critical temperature T IC = 21.7 K and 21.1 K for LiNiPO4 and LiNi0.9Co0.1PO4, respectively. The C and IC phases coexist over the temperature interval (20.6–20.8) K and (20.2–21.2) K in LiNiPO4 and LiNi0.9Co0.1PO4, respectively. In the LiNi0.9Mn0.1PO4 the magnetic phase transition occurs at T N = 22.7 K, but a magnetic scattering is observed up to 24.6 K.

Magneto-Optical Properties of Rare-Earth Terbium Ferrite-Garnet in the Near the Temperature of the Orientation Phase Transition

A model of the rearrangement of the domain structure of the Tb0.2Y2.8Fe5O12 garnet ferrite in the temperature region of the spontaneous reorientation of the easy magnetization axis is proposed, which makes it possible to consistently describe (at a qualitative level) the entire set of experimental results obtained. The latter makes it possible to make a choice in favor of the fluctuation mechanism of nucleation of domains of a new magnetic phase in the process of reorientation of the direction of the easy magnetization axis.

Intriguing Strain-Governed Magnetic Phase Transitions in 2D Vanadium Porphyrin Sheet

The strain effect on the magnetic response of the 2D materials as spintronic devices are always important in actual applications. Due to the intriguing electronic and magnetic properties of two-dimensional...

Синтез и оптические свойства кристаллов метабората меди, легированного никелем

This work presents information on the growth and spectroscopic study of single crystals of copper metaborate doped with nickel Cu1-xNixB2O4 (x = 0.05, 0.1). In the absorption spectra of both crystals, satellites related to Cu centers distorted by impurity Ni atoms were observed near the lines of zero phonon transitions. Polarization studies in the isotropic ab-plane of the tetragonal crystal Cu1-xNixB2O4 show the presence of linear magnetic dichroism in the magnetically ordered state, which was previously observed both in manganese-doped and undoped copper metaborates CuB2O4. The temperature of magnetic phase transitions into the collinear antiferromagnetic and into helicoidal structures, TN = 19.1 K and T* = 8.6 К, respectively, were determined from the temperature dependence of the dichroic signal.

Спиральное магнитное упорядочение и переход металл--диэлектрик в модели Хаббарда на треугольной решeтке

The magnetic phase diagrams of the two-dimensional Hubbard model for isotropic and anisotropic triangular lattices are constructed within the Hartree-Fock and slave boson approximations. The triangular lattice specific non-collinear and spiral magnetic states, as well as phase separation between them, are shown to be realized in a wide range of model parameters along with collinear magnetic states (stripe antiferromagnetic and ferromagnetic). Phase transitions of the first and second order are found, and the boundaries of the phase separation regions are determined. A comparison of the two approximations, Hartree-Fock and slave boson, shows that electronic correlations suppress magnetic states, the region of paramagnetism being expand, for values U/t>5. At the same time, when the Fermi level is near the van Hove singularity, electron correlations do not change the diagrams qualitatively, which is consistent with the previously obtained result for square and cubic lattices. The results are compared with the data available in the literature for other methods and approaches.

Magnetic Phase Diagram of the MnxFe2−xP1−ySiy System

The phase diagram of the magnetocaloric MnxFe2−xP1−ySiy quaternary compounds was established by characterising the structure, thermal and magnetic properties in a wide range of compositions (for a Mn fraction of 0.3 ≤ x < 2.0 and a Si fraction of 0.33 ≤ y ≤ 0.60). The highest ferromagnetic transition temperature (Mn0.3Fe1.7P0.6Si0.4, TC = 470 K) is found for low Mn and high Si contents, while the lowest is found for low Fe and Si contents (Mn1.7Fe0.3P0.6Si0.4, TC = 65 K) in the MnxFe2−xP1−ySiy phase diagram. The largest hysteresis (91 K) was observed for a metal ratio close to Fe:Mn = 1:1 (corresponding to x = 0.9, y = 0.33). Both Mn-rich with high Si and Fe-rich samples with low Si concentration were found to show low hysteresis (≤2 K). These compositions with a low hysteresis form promising candidate materials for thermomagnetic applications.