459 research outputs found
Magnetic anisotropy of YbNi4P2
We report on transport and magnetic measurements between 1.8 and 400 K on
single crystalline YbNi4P2, which was recently reported to be a heavy fermion
system with a low lying ferromagnetic transition at T_C=0.17 K, based on data
from polycrystals. The tetragonal crystal structure of YbNi4P2 presents
quasi-one-dimensional Yb chains along the c direction. Here we show that at
high temperatures, the magnetic anisotropy of YbNi4P2 is dominated by the
crystal electrical field effect with an Ising-type behaviour, which gets more
pronounced towards lower temperatures. The electrical resistivity also reflects
the strong anisotropy of the crystal structure and favours transport along c,
the direction of the Yb chains.Comment: SCES 2011 proceedings, in pres
Single crystal growth and anisotropy of CeRuPO
We report on the single crystal growth of the ferromagnetic Kondo lattice
system CeRuPO using a Sn flux method. Magnetic susceptibility and electrical
resistivity measurements indicate strong anisotropy of this structurally
layered compound. They evidence that the magnetic moments order
ferromagnetically along the c-direction of the tetragonal unit cell, whereas
the crystal electric field (CEF) anisotropy favors the ab-plane. Therefore,
CeRuPO presents the unusual case within rare earth systems, where the
anisotropy of the interionic exchange interaction overcomes the single ion
anisotropy due to the CEF interaction.Comment: 13 pages, 7 figures, high quality figures:
http://www.cpfs.mpg.de/~krellner
Single crystal growth and anisotropy of CeRuPO
We report on the single crystal growth of the ferromagnetic Kondo lattice
system CeRuPO using a Sn flux method. Magnetic susceptibility and electrical
resistivity measurements indicate strong anisotropy of this structurally
layered compound. They evidence that the magnetic moments order
ferromagnetically along the c-direction of the tetragonal unit cell, whereas
the crystal electric field (CEF) anisotropy favors the ab-plane. Therefore,
CeRuPO presents the unusual case within rare earth systems, where the
anisotropy of the interionic exchange interaction overcomes the single ion
anisotropy due to the CEF interaction.Comment: 13 pages, 7 figures, high quality figures:
http://www.cpfs.mpg.de/~krellner
Magnetic field dependence of the antiferromagnetic phase transitions in Co-doped YbRh_2Si_2
We present first specific-heat data of the alloy Yb(Rh_(1-x)Co_x)_2Si_2 at
intermediate Co-contents x=0.18, 0.27, and 0.68. The results already point to a
complex magnetic phase diagram as a function of composition. Co-doping of
YbRh_2Si_2 (T_N^{x=0}=72 mK) stabilizes the magnetic phase due to the volume
decrease of the crystallographic unit cell. The magnetic phase transitions are
clearly visible as pronounced anomalies in C^{4f}(T)/T and can be suppressed by
applying a magnetic field. Going from x=0.18 to x=0.27 we observe a change from
two mean-field (MF) like magnetic transitions at T_N^{0.18}=1.1 K and
T_L^{0.18}=0.65 K to one sharp \lambda-type transition at T_N^{0.27}=1.3 K.
Preliminary measurements under magnetic field do not confirm the field-induced
first-order transition suggested in the literature. For x=0.68 we find two
transitions at T_N^{0.68}=1.14 K and T_L^{0.68}=1.06 K.Comment: Accepted for the ICM proceedings 200
Development of the critical exponent at the antiferromagnetic phase transition of YbRh2Si2 under chemical pressure
We present specific-heat measurements in the vicinity of the
antiferromagnetic phase transition on single crystals of the alloy
Yb(Rh_{1-x}Co_x)2Si2 for x<= 0.38. This study was motivated by the violation of
critical universality in the undoped YbRh2Si2 (Krellner et al., Phys. Rev.
Lett. 102, 196402) where we have found a large critical exponent a=0.38. For
Co-doped samples we observe a drastic change of the critical fluctuations
resulting in a negative a, explainable within the universality classes of phase
transitions. The development of a under chemical pressure gives strong
indication that the violation of critical universality in YbRh2Si2 is due to
the nearby quantum critical point.Comment: Accepted for the QCNP proceedings 200
Physical properties and crystal chemistry of Ce2Ga12Pt
Single crystals of the new ternary compound Ce2Ga12Pt were prepared by the
self-flux technique. The crystal structure with the space group P4/nbm was
established from single-crystal X-ray diffraction data and presents a
derivative of the LaGa6Ni0.6 prototype. Magnetic susceptibility measurements
show Curie-Weiss behaviour due to local Ce^3+ moments. At high temperatures,
the magnetic anisotropy is dominated by the crystal-electric-field (CEF) effect
with the easy axis along the crystallographic c direction. Ce2Ga12Pt undergoes
two antiferromagnetic phase transitions at T_N,1 = 7.3K and T_N,2 = 5.5K and
presents several metamagnetic transitions for the magnetic field along c.
Specific-heat measurements prove the bulk nature of these magnetic transitions
and reveal a doublet CEF ground state. The 4f contribution to the resistivity
shows a broad maximum at T_max ~ 85K due to Kondo scattering off the CEF ground
state and excited levels.Comment: 12 pages, accepted in J. Phys.: Condens. Matte
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