18 research outputs found
Novel Field-Induced Phases in HoMnO3 at Low Temperatures
The novel field-induced re-entrant phase in multiferroic hexagonal HoMnO3 is
investigated to lower temperatures by dc magnetization, ac susceptibility, and
specific heat measurements at various magnetic fields. Two new phases have been
unambiguously identified below the Neel transition temperature, TN=76 K, for
magnetic fields up to 50 kOe. The existence of an intermediate phase between
the P[6]_3[c]m and P[6]_3c[m] magnetic structures (previously predicted from
dielectric measurements) was confirmed and the magnetic properties of this
phase have been investigated. At low temperatures (T<5 K) a dome shaped phase
boundary characterized by a magnetization jump and a narrow heat capacity peak
was detected between the magnetic fields of 5 kOe and 18 kOe. The transition
across this phase boundary is of first order and the magnetization and entropy
jumps obey the magnetic analogue of the Clausius-Clapeyron relation. Four of
the five low-temperature phases coexist at a tetracritical point at 2 K and 18
kOe. The complex magnetic phase diagram so derived provides an informative
basis for unraveling the underlying driving forces for the occurrence of the
various phases and the coupling between the different orders.Comment: 14 pages, 14 figure
Incompatible Magnetic Order in Multiferroic Hexagonal DyMnO3
Magnetic order of the manganese and rare-earth lattices according to
different symmetry representations is observed in multiferroic hexagonal (h-)
DyMnO by optical second harmonic generation and neutron diffraction. The
incompatibility reveals that the 3d-4f coupling in the h-MnO system (
= Sc, Y, In, Dy - Lu) is substantially less developed than commonly expected.
As a consequence, magnetoelectric coupling effects in this type of split-order
parameter multiferroic that were previously assigned to a pronounced 3d-4f
coupling have now to be scrutinized with respect to their origin
Magnetic properties of the frustated fcc antiferromagnet HoB12 above and below TN
We have investigated the magnetic ordering of the frustrated fcc antiferromagnet HoB12. Below TN 7.4K antiferromagnetic order and a complex phase diagram is observed. Above TN neutron scattering experiments show strong diffuse scattering. The diffuse signal indicates strong correlations between the rare earth moments along the [111] direction well above TN. The behavior of this component resembles low dimensional magnets which are known to show long range order only at T 0. Close to TN correlations perpendicular to the [111] direction get relevant, they diverge towards TN. Thus we observe a complex ordering process where the frustration is lifted in steps. The experimental data and their interpretation is presented, some of the possible microscopic origins are discusse
Probing multiferroicity and spin-spin interactions via dielectric measurements on Y-doped Ho
Perturbed angular correlations investigations on YMnO3 multiferroic manganite
International audienceThe Perturbed Angular Correlation (PAC) technique was applied to study the yttrium local environment in YMnO3 multiferroic manganite. The electric field gradients (EFG) at the Y site have been measured as function of temperature, covering both ferroelectric and magnetic transitions. The results were compared with point charge model (PCM) calculations. The experimental results show two different EFG distributions for all temperatures. Only one can be directly attributed to the yttrium crystalline site in the hexagonal structure