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Lecture Nadang Mufti


03 February 2011 FWN-Building 5111.0006, Nijenborgh 4, 9747 AG, Groningen
Speaker: Dr. Nadang Mufti
Affiliation: Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
Title: Fe-magnetism, structural distortion, spin frustration and quantum critical point in AFe4 X 2 compounds
Date: Thu Feb 3, 2011
Start: 14.30
Location: FWN-Building 5111.0006
Host: G.R. Blake
Telephone: +31 50 363 4440


The compound RFe4Ge2 (R = Dy, Ho, Er, Y ) is reported to crystallize with the tetragonal ZrFe4Si2 type structure (space group P42/mnm) and show interesting magnetic properties. The relationship between the rare-earth and Fe magnetic ordering in this system has been investigated by P. Shobinger-Papamantellos et al. using neutron diffraction [1]. In the case of YFe4Ge2, antiferromagnetic ordering with a small ordered moment of ~0.63 μB occurs simultaneously with a large first-order structural distortion (~ 2.5%) from tetragonal to orthorhombic symmetry at 43.5 K. The presence of a large structural distortion despite weak antiferromagnetic ordering with low T N and small magnetic moments is reminiscent of observations in the Fe-arsenides. Therefore, we are interested in investigating the relationship between the magnetic Fe-order, spin frustration and the structural transition in this system, and in how the magnetism and structural instability change upon doping with smaller R-atoms. Here, we will present the magnetic and structural properties of RFe4 X 2 (R = Y, Sc, Lu and Zr with X = Ge and Si) based on magnetic susceptibility, specific heat, resistivity, Mössbauer spectroscopy and low temperature X-ray diffractometer measurements. Our results indicate the occurrence of a transition in all compounds at a critical temperature between 30 K and 75 K. There is no systematic relationship between T N and the lattice parameters of RFe4 X 2. However, the magnetic order, spin frustration and structural distortion seem generally to be connected.


1.  P. Shobinger-Papamantellos et al., J. Magn. Magn. Mater. 310, 63 (2007).


Last modified:22 October 2012 2.31 p.m.