Browsing by Author "Cheong, S-W."

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Symmetry of multiferroicity in a frustrated magnet TbMn2O5
(2007-04-13)
Okamoto, J.
;
Huang, D. J.
;
Mou, C. -Y.
;
Chao, K. S.
;
Lin, H. -J.
Based on measurements of soft-x-ray magnetic scattering and symmetry considerations, we demonstrate that the magnetoelectric effect in TbMn2O5 arises from an internal field determined by (S) over right arrow ((q) over right arrow) x (s) over right arrow (-(q) over right arrow) with (S) over right arrow ((q) over right arrow) being the magnetization at modulation vector (q) over right arrow, whereas the magnetoelastic effect in the exchange energy governs the response to external electric fields. Our results set fundamental symmetry constraints on the microscopic mechanism of multiferroicity in frustrated magnets.
Thermally or Magnetically Induced Polarization Reversal in the Multiferroic CoCr(2)O(4)
(2009-02-13)
Choi, Y. J.
;
Okamoto, J.
;
Huang, D. J.
;
Chao, K. S.
;
Lin, H. J.
We report the unexpected evolution, with thermal and magnetic-field (H) variations, of the interrelation between the polarization P, magnetization M, and spiral wave vector Q in CoCr(2)O(4), which has a ferrimagnetic conical-spiral magnetic order. For example, P suddenly jumps and changes its sign at the magnetic lock-in transition (T(L)) with thermal variation, or with isothermal variation of H (without changing its direction) at T(L), which surprisingly occurs without change in spiral handedness (i.e., the sign of Q). The presence of multiple spiral sublattices may be behind this unusual behavior.
Thermally or Magnetically Induced Polarization Reversal in the Multiferroic CoCr2O4
(2009-02-13)
Choi, Y. J.
;
Okamoto, J.
;
Huang, D. J.
;
Chao, K. S.
;
Lin, H. J.
We report the unexpected evolution, with thermal and magnetic-field (H) variations, of the interrelation between the polarization P, magnetization M, and spiral wave vector Q in CoCr2O4, which has a ferrimagnetic conical-spiral magnetic order. For example, P suddenly jumps and changes its sign at the magnetic lock-in transition (T-L) with thermal variation, or with isothermal variation of H (without changing its direction) at T-L, which surprisingly occurs without change in spiral handedness (i.e., the sign of Q). The presence of multiple spiral sublattices may be behind this unusual behavior.