7 research outputs found
Ferromagnetic ordering along the hard axis in the Kondo lattice YbIr3Ge7
Ferromagnetic Kondo lattice compounds are far less common than their
antiferromagnetic analogs. In this work, we report the discovery of a new
ferromagnetic Kondo lattice compound, YbIr3Ge7. Like almost all ferromagnetic
Kondo lattice systems, YbIr3Ge7 shows magnetic order with moments aligned
orthogonal to the crystal electric field (CEF) easy axis. YbIr3Ge7 is unique in
that it is the only member of this class of compounds that crystallizes in a
rhombohedral structure with a trigonal point symmetry of the magnetic site, and
it lacks broken inversion symmetry at the local moment site. AC magnetic
susceptibility, magnetization, and specific heat measurements show that
YbIr3Ge7 has a Kondo temperature TK = 14 K and a Curie temperature TC = 2.4 K.
Ferromagnetic order occurs along the crystallographic [100] hard CEF axis
despite the large CEF anisotropy of the ground state Kramers doublet with a
saturation moment along [001] almost four times larger than the one along
[100]. This implies that a mechanism which considers the anisotropy in the
exchange interaction to explain the hard axis ordering is unlikely. On the
other hand, the broad second-order phase transition at TC favors a
fluctuation-induced mechanism
CeIrGe: a local moment antiferromagnetic metal with extremely low ordering temperature
CeIrGe is an antiferromagnetic metal with a remarkably low ordering
temperature = 0.63 K, while most Ce-based magnets order between 2
and 15 K. Thermodynamic and transport properties as a function of magnetic
field or pressure do not show signatures of Kondo correlations, interaction
competition, or frustration, as had been observed in a few antiferromagnets
with comparably low or lower . The averaged Weiss temperature
measured below 10 K is comparable to suggesting that the RKKY
exchange coupling is very weak in this material. The unusually low
in CeIrGe can therefore be attributed to the large Ce-Ce bond length of
about 5.7 {\AA}, which is about 1.5 {\AA} larger than in the most Ce-based
intermetallic systems.Comment: 4 figure
Anomalous metamagnetism in the low carrier density Kondo lattice YbRh3Si7
We report complex metamagnetic transitions in single crystals of the new low
carrier Kondo antiferromagnet YbRh3Si7. Electrical transport, magnetization,
and specific heat measurements reveal antiferromagnetic order at T_N = 7.5 K.
Neutron diffraction measurements show that the magnetic ground state of
YbRh3Si7 is a collinear antiferromagnet where the moments are aligned in the ab
plane. With such an ordered state, no metamagnetic transitions are expected
when a magnetic field is applied along the c axis. It is therefore surprising
that high field magnetization, torque, and resistivity measurements with H||c
reveal two metamagnetic transitions at mu_0H_1 = 6.7 T and mu_0H_2 = 21 T. When
the field is tilted away from the c axis, towards the ab plane, both
metamagnetic transitions are shifted to higher fields. The first metamagnetic
transition leads to an abrupt increase in the electrical resistivity, while the
second transition is accompanied by a dramatic reduction in the electrical
resistivity. Thus, the magnetic and electronic degrees of freedom in YbRh3Si7
are strongly coupled. We discuss the origin of the anomalous metamagnetism and
conclude that it is related to competition between crystal electric field
anisotropy and anisotropic exchange interactions.Comment: 23 pages and 4 figures in the main text. 7 pages and 5 figures in the
supplementary materia