Solovyev I.V.,Japan National Institute of Materials Science |
Pchelkina Z.V.,RAS Institute of Metal Physics
Physical Review B - Condensed Matter and Materials Physics | Year: 2010
We present the microscopic theory of improper multiferroicity in BiMnO 3, which can be summarized as follows: (1) the ferroelectric polarization is driven by the hidden antiferromagnetic order in the otherwise centrosymmetric C2/c structure; (2) the relativistic spin-orbit interaction is responsible for the canted spin ferromagnetism. Our analysis is supported by numerical calculations of electronic polarization using the Berry-phase formalism, which was applied to the low-energy model of BiMnO3 derived from the first-principles calculations. We explicitly show how the electric polarization can be controlled by the magnetic field and argue that BiMnO3 is a rare and potentially interesting material where ferroelectricity can indeed coexist and interplay with the ferromagnetism. © 2010 The American Physical Society.
Solin N.I.,RAS Institute of Metal Physics
Journal of Experimental and Theoretical Physics | Year: 2012
The nature of the electrical resistivity for low-doped lanthanum manganites is elucidated. The electrical resistivity is described by the Efros-Shklovskii law (inρ ∞ (T 0/T) -1/2, where T 0 ∞ 1/R is) in the temperature range from T* ≈ 300 K ≈ T C (T C is the Curie temperature for conducting manganites) to their T C and is explained by the tunneling of carriers between localized states. The magnetoresistance is explained by a change in the size of localized states R is in a magnetic field. The patterns of change in R is with temperature and magnetic field strength determined from magnetotransport properties are satisfactorily described in the model of phase separation into small-radius metallic droplets in a paramagnetic matrix. The sizes R is and their temperature dependence have been estimated through magnetic measurements. The results confirm the existence of a Griffith phase. The intrinsic inhomogeneities produced by thermodynamic phase separation determine the electrical resistivity and magnetoresistance of lanthanum manganites. © Pleiades Publishing, Inc., 2012.
Kuchin A.G.,RAS Institute of Metal Physics
Journal of Magnetism and Magnetic Materials | Year: 2010
Magnetic properties of the single-crystalline Lu2Fe17-xMnx compounds, in which x=0, 0.5, and 2, with the Th2Ni17-type crystal structure are reported. The Lu2Fe17-xMnx compounds with x=0 and 0.5 are ferromagnets at low temperatures and antiferromagnets at high temperatures. The compound with x=2 is always a ferromagnet. The easy-plane magnetic anisotropy in the Lu2Fe17-xMnx ferromagnets drastically weakens with increase in Mn content up to x=2. The temperature dependence of the first magnetic anisotropy constant was obtained and compared with the single-ion model prediction. © 2010 Elsevier B.V. All rights reserved.
Irkhin V.Yu.,RAS Institute of Metal Physics
Journal of Physics Condensed Matter | Year: 2011
A scaling consideration of the Kondo lattices is performed with account of logarithmic Van Hove singularities (VHS) in the electron density of states. The scaling trajectories are presented for different magnetic phases. It is demonstrated that VHS lead to a considerable increase of the non-Fermi-liquid behavior region owing to softening of magnon branches during the renormalization process. Although the effective coupling constant remains moderate, the renormalized magnetic moment and spin-fluctuation frequency can decrease by several orders of magnitude. A possible application to f-systems and weak itinerant magnets is discussed. © 2011 IOP Publishing Ltd.
Bebenin N.G.,RAS Institute of Metal Physics
Physics of Metals and Metallography | Year: 2011
A brief review of properties of the ferromagnetic manganites La 1 - x Ca x MnO3 is given. Lattice properties, magnetic properties, transport phenomena, magnetic resonance, and the results of neutron diffraction and optical studies are considered. Special attention is paid to effects observed near the Curie temperature. © Pleiades Publishing, Ltd., 2011.