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Register a new userMagnetic anisotropy, first-order-like metamagnetic transitions and large negative magnetoresistance in the single crystal of Gd$_{2}$PdSi$_3$
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Electrical resistivity ($rho$), magnetoresistance (MR), magnetization, thermopower and Hall effect measurements on the single crystal Gd$_{2}$PdSi$_3$, crystallizing in an AlB$_2$-derived hexagonal structure are reported. The well-defined minimum in $rho$ at a temperature above Neel temperature (T$_N$= 21 K) and large negative MR below $sim$ 3T$_N$, reported earlier for the polycrystals, are reproducible even in single crystals. Such features are generally uncharacteristic of Gd alloys. In addition, we also found interesting features in other data, e.g., two-step first-order-like metamagnetic transitions for the magnetic field along [0001] direction. The alloy exhibits anisotropy in all these properties, though Gd is a S-state ion.
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For the skyrmion-hosting intermetallic Gd$_2$PdSi$_3$ with centrosymmetric hexagonal lattice and triangular net of rare earth sites, we report a thorough investigation of the magnetic phase diagram. Our work reveals a new magnetic phase with isotropic value of the critical field for all orientations, where the magnetic ordering vector $mathbf{q}$ is depinned from its preferred directions in the basal plane. This is in contrast to the highly anisotropic behavior of the low field phases, such as the skyrmion lattice (SkL), which are easily destroyed by in-plane magnetic field. The bulk nature of the SkL and of other magnetic phases was evidenced by specific-heat measurements. Resistivity anisotropy, likely originating from partial gapping of the density of states along $mathbf{q}$ in this RKKY magnet, is picked up via the planar Hall effect (PHE). The PHE confirms the single-$mathbf{q}$ nature of the magnetic order when the field is in the hexagonal plane, and allows to detect the preferred directions of $mathbf{q}$. For field aligned perpendicular to the basal plane, several scenarios for the depinned phase (DP), such as tilted conical order, are discussed on the basis of the data.
We report on large negative magnetoresistance observed in ferromagnetic thiospinel compound CuCrZrS$_{4}$. Electrical resistivity increased with decreasing temperature according to the form proportional to $textrm{exp}(T_{0}/T)^{1/2} $, derived from variable range hopping with strong electron-electron interaction. Resistivity under magnetic fields was expressed by the same form with the characteristic temperature T0 decreasing with increasing magnetic field. Magnetoresistance ratio $rho (T,0)/rho(T,H)$ is 1.5 at 100 K for H=90 kOe and increases divergently with decreasing temperature reaching 80 at 16 K. Results of magnetization measurements are also presented. Possible mechanism of the large magnetoresistance is discussed.
In this paper, the magnetic and transport properties were systematically studied for EuAg$_4$As$_2$ single crystals, crystallizing in a centrosymmetric trigonal CaCu$_4$P$_2$ type structure. It was confirmed that two magnetic transitions occur at $textit{T}$$_{N1}$ = 10 K and $textit{T}$$_{N2}$ = 15 K, respectively. With the increasing field, the two transitions are noticeably driven to lower temperature. At low temperatures, applying a magnetic field in the $textit{ab}$ plane induces two successive metamagnetic transitions. For both $textit{H}$ $parallel$ $textit{ab}$ and $textit{H}$ $parallel$ $textit{c}$, EuAg$_4$As$_2$ shows a positive, unexpected large magnetoresistance (up to 202%) at low fields below 10 K, and a large negative magnetoresistance (up to -78%) at high fields/intermediate temperatures. Such anomalous field dependence of magnetoresistance may have potential application in the future magnetic sensors. Finally, the magnetic phase diagrams of EuAg$_{4}$As$_{2}$ were constructed for both $textit{H}$ $parallel$ $textit{ab}$ and $textit{H}$ $parallel$ $textit{c}$.
We grew the single crystal of stoichiometric Tm5Si2.0Ge2.0 using a Bridgeman method and performed XRD, EDS, magnetization, ac and dc magnetic susceptibilities, specific heat, electrical resistivity and XPS experiments. It crystallizes in orthorhombic Sm5Ge4-type structure. The mean valence of Tm ions in Tm5Si2.0Ge2.0 is almost trivalent. The 4f states is split by the crystalline electric field. The ground state exhibits the long range antiferromagnetic order with the ferromagnetically coupled magnetic moments in the ac plane below 8.01 K, while the exited states exhibit the reduction of magnetic moment and magnetic entropy and -log T-behaviors observed in Kondo materials.
We report neutron diffraction and magnetization studies of the magnetic order in multiferroic BiFeO3. In ferroelectric monodomain single crystals, there are three magnetic cycloidal domains with propagation vectors equivalent by crystallographic symmetry. The cycloid period slowly grows with increasing temperature. The magnetic domain populations do not change with temperature except in the close vicinity of the N{P}eel temperature, at which, in addition, a small jump in magneti- zation is observed. No evidence for the spin-reorientation transitions proposed in previous Raman and dielectric studies is found. The magnetic cycloid is slightly anharmonic for T=5 K. The an- harmonicity is much smaller than previously reported in NMR studies. At room temperature, a circular cycloid is observed, within errors. We argue that the observed anharmonicity provides important clues for understanding electromagnons in BiFeO3.
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