Magnetodielectric effect in theS=1∕2quasi-two-dimensional antiferromagnetK2V3

Abstract

We report the optical and magneto-optical properties of K2V3O8, an S=1/2 quasi-twodimensional Heisenberg antiferromagnet. Local spin density approximation electronic structure calculations are used to assign the observed excitations and analyze the field dependent features. Two large magneto-optical effects, centered at ∼1.19 and 2.5 eV, are attributed to field-induced changes in the V 4+ d → d on-site excitations due to modification of the local crystal field environment of the VO5 square pyramids with applied magnetic field. Taken together, the evidence for a soft lattice, the presence of vibrational fine structure on the sharp 1.19 eV magneto-optical feature, and the fact that these optical excitations are due to transitions from a nearly pure spin polarized V d state to hybridized states involving both V and O, suggest that the magneto-dielectric effect in K2V3O8 is driven by strong lattice coupling.

Magneto-optical investigation of the field-induced spin-glass-insulator to ferromagnetic-metal transition in the bilayer manganite(La0.4Pr0.6)1.2Cao1, Haraldsen2, Rai3 et al. 2006Phys. Rev. BSelf Cite

“…However, at this time, most magnetodielectric materials 9,10,11,12,13,14,15,16,19,20,23 display contrast only at low temperatures. Strategic control of spin-lattice interactions or the presence of a magnetically-driven phase transition (and associated change in ground state) offer potential routes to higher transition temperatures.…”

“…6,7,8 These materials are therefore wellsuited for fundamental magnetodielectric properties investigations. 9,10,11,12,13,14,15,16,17,18,19,20,21,22,23 They are also useful to extend the Tomioka-Tokura electronic phase diagram picture 24 and test oscillator strength sum rules.…”

Coupling of spin and lattice modes in theS=1/2two-dimensional antiferromagnet K2V

“…We find no evidence for the presence of a Raman-active soft mode related to the structural phase transition at 110 K. The observed soft mode is assigned to the torsional mode that flexes the VO 5 square pyramids out of the plane, which could not be detected by optical spectroscopy. 12 Here we note that the layer compound SrCu 2 (BO 3 ) has a soft mode at 62 cm −1 as an in-phase motion of almost all ions along an out-of-plane direction. 25 This soft mode is a consequence of a continuous corrugation of the Cu-BO 3 layer.…”

Electronic structure and bond competition in the polar magnetPbVO3

“…These vanadyl containing compouds are local moment magnets due to the formation of spin 1/2 moments on the V ions, and are band insulators, The band gaps are formed by a combination of strong crystal field splitting associated with the short V-O distance, and on-site Hund's coupling, which exchange splits the 1/2 filled V non-bonding orbital. 19,20 Thus, perovskite vanadates offer the possibility of combining a magnetic B-site ion with insulating behavior and stereochemical activity on both the A and B-sites. This was recently realized by the high pressure synthesis of PbVO 3 .…”