36 research outputs found
Magnetodielectric coupling in a Ru-based 6H-perovskite, Ba3NdRu2O9
A large spin-orbit coupling is a way to control strong magnetodielectric (MD)
coupling in a higher d-orbital materials. However reports are rare on such
compounds due to often leaky conductive behavior. Here, we demonstrate MD
coupling in a Ru-based 6H-perovskite system, Ba3NdRu2O9. The rare-earth ion in
a 6H-perovskite makes the system insulating enough to carry out MD
investigation. The compound is ferromagnetically ordered below 24 K (TC),
followed by another magnetic feature at T~ 17 K (T2). The dielectric constant
clearly traces the magnetic ordering, manifesting a peak at the onset of TC,
which is suppressed by the application of an external magnetic field (H). The
results indicate the presence of MD coupling in this compound, which is further
confirmed by the H-dependence of the dielectric constant. Interestingly, a
cross-over of the sign of MD coupling is observed at T ~ T2. We conclude that
two different mechanism controls the MD coupling which yields positive and
negative coupling, respectively. Both mechanisms are competing as a function of
temperature and magnetic field. This brings us a step closer to design and
control the magnetodielectric effect in 6H-perovskites containing higher
d-orbital elements
Magnetic and magnetodielectric coupling anomalies in the Haldane spin-chain system Nd2BaNiO5
We report the magnetic, heat-capacity, dielectric and magnetodielectric (MDE)
behaviour of a Haldane spin-chain compound containing light rare-earth ion,
Nd2BaNiO5, in detail, as a function of temperature (T) and magnetic field (H)
down to 2 K. In addition to the well-known long range antiferromagnetic order
setting in at (T_N=) 48 K as indicated in dc magnetization (M), we have
observed another magnetic transition near 10 K; this transition appears to be
of a glassy-type which vanishes with a marginal application of external
magnetic field (even H= 100 Oe). There are corresponding anomalies in
dielectric constant as well with variation of T. The isothermal M(H) curves at
2 and 5 K reveal the existence of a magnetic-field induced transition around 90
kOe; the isothermal H-dependent dielectric constant also tracks such a
metamagnetic transition. These results illustrate the MDE coupling in this
compound. Additionally, we observe a strong frequency dependence of a step in
T-dependent dielectric constant with this feature appearing around 25-30 K for
the lowest frequency of 1 kHz, far below T_N. This is attributed to interplay
between crystal-field effect and exchange interaction between Nd and Ni, which
establishes the sensitivity of dielectric measurements to detect such effects.
Interestingly enough, the observed dispersions of the T-dependent dielectric
constant curves is essentially H-independent in the entire T-range of
measurement, despite the existence of MDE coupling, which is in sharp contrast
with other heavy rare-earth members in this series.Comment: AIP Advances, in Press. Supplementary Material is include