- Michal Vališka: Variations of magnetism in UIrGe in magnetic fields and external pressures
- 5. 4. 2017, 14:30
- lecture room F2, first floor Ke Karlovu 5
- more information
Abstract:
UIrGe crystallizes in the orthorhombic TiNiSi-type structure. It exhibits antiferromagnetic (AF) ordering of strongly reduced U magnetic moments (0.36 µB at 1.8 K) below TN ~ 16 K. The AF structure is non-collinear with a non-zero a-axis AF component [1,2]. Application of a magnetic field along the c-axis leads to a metamagnetic transition (MT) with a critical field of ~ 14 T at 2 K [3]. The AF structure is consequently destroyed and all the U moments point along the field direction [4]. A similar MT is induced around ~ 21 T (at 2 K) applied along b [3].
We have grown a new UIrGe single crystal and measured on it the magnetization, specific heat, electrical resistivity/magnetoresistance thermal expansion/magnetostriction with respect to temperature and magnetic field applied along the main crystallographic axes. The observed temperature dependences of electrical resistivity (thermal expansion) are strongly anisotropic with respect to the direction of applied electrical current (linear expansion). The magnetoresistance (magnetostriction) anomalies associated with MT exhibit pronounced anisotropy with respect to the direction of applied magnetic field. The results will be discussed in the light of known ground state and the MT transition to the high-field state with magnetic moment aligned along c published by Prokeš et al. [4].
Ehrenfest relations applied on the heat capacity and thermal expansion data suggest very small pressure dependence of the TN. This was confirmed by measurement of heat capacity and electrical resistivity under pressure up to 3 GPa. Application of hydrostatic pressures around 12 GPa leads to a collapse of the magnetic order [5].
[1] V. Sechovský, L. Havela, in: K.H.J. Buschow (Ed.), Handbook of Magnetic Materials, vol. 11, North Holland, Amsterdam, 1998, p. 1 and references therein
[2] K. Prokeš et al., Physica B 350 (2004) e199.
[3] S. Yoshii, J. Phys. Conf. Ser. 51 (2006) 151.
[4] K. Prokeš et al., J. Phys.: Condens. Matter 20 (2008) 104221.
[5] J. Pospíšil et al., J. Phys. Soc. Jpn 86, (2017) 044709.