7-11 July 2014
Africa/Johannesburg timezone
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Pressure effects on the magnetic behavior of the local moment ferromagnet CeCuSi

Presented by Prof. GIOvanni HEARNE on 9 Jul 2014 from 17:10 to 19:00
Type: Poster Presentation
Session: Poster2
Track: Track A - Division for Physics of Condensed Matter and Materials
Board #: A.248


Interest in Ce or U based ternary intermetallics has been ongoing for the last three decades, because they show a variety of exotic magnetic-electronic ground-states (e.g. heavy fermion behavior , non Fermi-liquid characteristics, etc). Most magnetic Ce<i>TX</i> compounds order antiferromagnetically (<i>T</i> is a transition-metal and <i>X</i> is a <i>p</i>-band element). One candidate, CeCuSi, is among a select number that exhibits ferromagnetic ordering at low temperatures; other candidates being CePd<i>X</i> (<i>X</i> = P, As, Sb). The ferromagnetic transition in this compound has been established from both specific heat data (&lambda;-type anomaly manifested at T<sub>C</sub> =15 K) and magnetization measurements in which an ordered moment of ~1 &mu;<sub>B</sub> has been obtained. The hybridization (<i>J</i>) between the localized 4<i>f</i> and more extended <i>d</i> orbitals (Ce 5<i>d</i> and <i>T</i> 3<i>d</i>), which influences intersite magnetic ordering of Ce moments via the RKKY indirect interaction mechanism involving the <i>d</i> conduction electrons, is readily tuned under pressure. Consequently new ground states can be stabilized at reduced inter-atomic spacing without the complexity of disorder from doping. Many well known antiferromagnetic Ce<i>TX</i> compounds have been the focus of attention in pressure studies in the last decade. There has been much less done, if any, in elucidating the pressure response of <i>ferromagnetic</i> analogs. We present the results of our pressure studies on the title compound. These studies have entailed : (i) SQUID magnetization measurements to ~10 GPa in a turn-buckle magnetic diamond anvil cell (TM-DAC) to monitor both T<sub>C</sub> and magnetic susceptibility, (ii) x-ray absorption spectroscopy (XAS) at the Ce <i>L</i><sub>3</sub>-edge (~5.7 keV) to pressures of ~16 GPa. The latter necessitates use of “perforated” diamond anvils in a membrane-DAC for both a near edge spectroscopy (XANES) probe of Ce valence and x-ray absorption dichroism (XMCD ) at 6 K to monitor shell-specific 5<i>d</i>-3<i>d</i> conduction electron spin polarization in the magnetically ordered state. We evidence increasing T<sub>C</sub> values (from 15 K to 30 K), and yet collapse of the XMCD signal, with rising pressure up to 10 GPa; beyond which signatures of a valence change are manifest in the XANES profiles.








Room: D Ring ground level

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