36 research outputs found
Magneto and ferroelectric phase transitions in HoMn2O5 monocrystals
From the physical point of view multiferroics present an extremely
interesting class of systems and problems. These are essentially of two kinds.
One is what are the microscopic conditions, and sometimes constrains, which
determine the possibility to combine in one system both magnetic and
ferroelectric properties. This turned out to be a quite nontrivial question,
and usually, in conventional systems, these two phenomena tend to exclude one
another. Why it is the case is an important and still not completely resolved
issue. In the present article we report our results from magnetic properties
measurements on HoMn2O5 with short discussion about it possible origin
Frustrated minority spins in GeNi2O4
Recently, two consecutive phase transitions were observed, upon cooling, in
an antiferromagnetic spinel GeNiO at K and
K, respectively \cite{matsuno, crawford}. Using unpolarized and polarized
elastic neutron scattering we show that the two transitions are due to the
existence of frustrated minority spins in this compound. Upon cooling, at
the spins on the \kagome planes order ferromagnetically in the
plane and antiferromagnetically between the planes (phase I), leaving the spins
on the triangular planes that separate the \kagome planes frustrated
and disordered. At the lower , the triangular spins also order in the
plane (phase II). We also present a scenario involving exchange
interactions that qualitatively explains the origin of the two purely magnetic
phase transitions
Order Parameters and Phase Diagrams of Multiferroics
The symmetry properties, order parameters, and magnetoelectric phase diagrams
of multiferroics are discussed. After brief reviews of NiVO,
TbMnO, and RbFe(MoO), we present a detailed analysis of
RMnO (with R=Y, Ho, Dy, Er, Tb, Tm).Comment: 23 pages, 7 figures, 3 tables. For FOCUS ON MULTIFERROICS (IOP