Papers by Keyword: Antiferromagnetism

Abstract: The temperature dependence of electronic and magnetic properties of the organic charge-transfer salt (DOEO)₄[HgBr₄]·TCE was investigated using magnetometry. The magnetic susceptibility shows a maximum at 40 K followed by an onset of a pronounced increase at 70 K and a constant behavior above 120 K. Implications on the charge carrier density are discussed. Combining the magnetometry with resistivity and ESR measurements we propose a sequence of insulating, metallic and semiconducting behavior with increasing temperature. Our results indicate that (DOEO)₄[HgBr₄]·TCE is close to the boundary between an insulating and conducting ground state.

Abstract: In this investigations the systems of the nanoparticles with competing exchange interactions are considered. The critical concentrations and possible types of magnetic states of particles in the case of direct exchange and RKKY interaction in the framework of the random interaction field method are determined. It is observed that in magnetic materials with the competition of the direct and indirect exchanges changing the type of ordering is possible at the change in the intensity of the indirect exchange under the influence of external factors.

Abstract: Influence of Ru substitution on magnetic properties of Y₂Fe₁₇ and Y₂Co₁₇ (hexagonal structure of the Th₂Ni₁₇-type) has been studied on single-crystalline samples. Whereas in the Y₂Fe_17-xRu_x system ferromagnetism is transformed rapidly into antiferromagnetism with a field-induced metamagnetic transition, in Y₂Co_17-xRu_x only a monotonous decrease of spontaneous magnetic moment, Curie temperature and first anisotropy constant is observed.

Abstract: At ambient pressure, the Fe_0.49(Rh_1-xPd_x)_0.51 alloys with the Pd concentration within 0 < x < 0.12 exhibit an antiferromagnetic (AF) state below the critical temperature T_t, while above x = 0.12 the alloys have a ferromagnetic (F) order up to the Curie temperature T_C 650 K. The temperature and field dependences of the magnetization in the alloys with x = 0.08; 0.13 were investigated under hydrostatic pressure up to 10 kbar. The application of pressure of about 8.5 kbar is observed to induce the F-AF phase transition in the ferromagnetically ordered compound with x = 0.13. The AF-F-AF phase evolution was revealed with increasing pressure in the AF-ordered alloy with x = 0.08.

Abstract: The realization of ferromagnetism or ferrimagnetism in BiCrO3 is crucial for its potential application in magnetoelectronic devices. It is known from experiment that the antiferromagnetic monoclinic phase of BiCrO3 transits to orthorhombic as pressure beyond 1GPa. Here, we present a first-principles study of the magnetism of orthorhombic BiCrO3 under pressures up to 80GPa. We find that the energy difference between its ferromagnetic phase and the ground state of G-type anti-ferromagnetic phase becomes greater as the pressure increases, as well as the estimated magnetic transition temperature TN. This implies the difficulty of transforming BiCrO3 into ferromagnetism by external pressure, and thus other approaches (such as doping magnetic ions) are necessary to explore its potential application in magnetoelectronic devices.

Abstract: It is pointed out that the most important open question posed by the anomalous uncompensated magnetic moment of nanosized antiferromagnets is largely overlooked today, 54 years after Richardson’s discovery of the phenomenon and 49 years after Néel’s explanation of it.

Abstract: TlFe2Se2-δ was synthesized by a self-flux method with excess amount of selenium. Elemental analysis using energy-dispersive X-ray spectroscopy estimates the deficiency δ at about 0.5. The magnetic susceptibility reveals an antiferromagnetic transition at TN ≈ 475 K. The resistivity exhibits a semiconducting behavior with an activation energy, EA = 0.04 eV. There is a clear anomaly in the resistivity at TN, indicating a strong interplay between magnetism and electric conduction.

Abstract: In a trigonal easy-plane -Fe2O3 antiferromagnet magnetic-field-dependent conic refraction due to the renormalization of the coefficients of elasticity effective magnetoelastic interaction is experimentally found in addition to the conventional internal conic refraction of the transverse elastic waves propagating along the trigonal C3 axis. It is shown that the deflection angle () of the energy flow from the C3 axis upon the internal conic refraction does not depend on the value of the magnetic field applied in the basis plane (HC3) and is a constant value determined by the correlation of the C14 and C44 coefficients of elasticity. The deflection angle of the energy flow upon the antiferromagnetic conic refraction () increases with increase in the field and tends to the  value at large H values. The obtained results agree well with the theory of this phenomenon in antiferromagnets and support its conclusions.

Abstract: NiFe2O4, ZnFe2O4 and Ni0.64Zn0.36Fe2O4 were prepared by a chemical co-precipitation method. The positive ferrite ZnFe2O4 usually exhibits antiferromagnetism. The magnetization of Ni0.64Zn0.36Fe2O4 is much larger than that of NiFe2O4, which can be explained by doping with nonmagnetic cations or cations with weak magnetization in an inverse spinal ferrite if these cations occupy A sites, the magnetic moment of Fe3+ ions at the B sites would be oriented in the same direction. Experimental values found for the molecular magnetic moments of NiFe2O4 and Ni0.64Zn0.36Fe2O4 were lower than their theoretic values because surface structure defects resulted in a magnetic spin glass structure.

Abstract: Definite regularity in the distribution of ferromagnetic, antiferromagnetic and superconducting elements is observed in the periodic table starting with the 4-th period. These trends were explained by distinction of degree of division of the d (f)- or р-orbitals of neighboring atoms in the crystal. We calculated also the radii of the external d (f)- and р-orbitals and the nearest to them orbitals with the Slater’s method. It is demonstrated that in the superconducting crystals the d-shells approach the nucleus of neighboring atoms are much closely those for ferromagnetic or antiferromagnetic crystals.