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H. Michor, V. Levytskyy, V. Babizhetskyy, M. Hembara, A. Schumer, S. Özcan, B.Ya. Kotur:
"MAGNETIC PROPERTIES OF SOLID SOLUTIONS HoCo_1-xNi_xC₂";
Talk: 16th Czech and Slovak Conference on Magnetism (CSMAG´16), Kosice, Slovakia; 2016-06-13 - 2016-06-17.

Ternary carbides RNiC₂ (R = La, .. Lu) and RCoC₂ (R = Nd, .. Lu) crystallize in the non-centrosymmetric orthorhombic CeNiC2-type structure, space group Amm2 [1,2]. These compounds attracted attention because of various interesting properties such as exotic superconductivity in LaNiC₂ (e.g. [3]), observation of charge density wave (CDW) formation related to Fermi surface nesting features in RNiC₂ with R = Pr, .. Tb, and its interplay with rare earth magnetism [4].
In the present study, we report on crystallographic characteristics, magnetic properties, heat capacity and electrical resistivity of a series of polycrystalline solid solutions HoCo_1-xNi_xC₂ (0 ≤ x ≤ 1) as well as studies on a HoCoC₂ single crystal grown by the Czochralski technique. Corresponding single crystal data of HoNiC2 are available in literature [5]. While the latter shows complex antiferromagnetic order at T_N~2.8 K, HoCoC₂ displays a ferromagnetic ground state with T_C=10.6 K. The evolution of magnetic ordering in the solid solution HoCo_1-xNi_xC₂ indicates a competing nature of these two order parameters and an important influence of crystal field effects. The latter causes a strongly reduced magnitude of the magnetic specific heat anomalies. We are using an approach based on modelling of crystal field and exchange coupling parameters in order to analyse the available magnetic susceptibility and magnetisation data as well as magnetic entropy data evaluated from specific heat measurements.
Our electrical resistivity data of HoNiC₂ further reveal an anomaly at about room temperature which indicates the formation of a CDW state. The transition temperature appears in line with the trend of CDW anomalies reported in Refs. [4] for related compounds RNiC₂ with R = Pr, .. Tb.
[1] O. I. Bodak, E. P. Marusin, V. A. Bruskov, Sov. Phys. Crystallogr. 25 (1980) 355.
[2] W. Jeitschko, M. H. Gerss, J. Less-Common Met.116 (1986) 147.
[3] T. Yanagisawa and I. Hase, J. Phys. Soc. Jpn. (JPSJ) 81 (2012) SB039.
[4] M. Murase et al., JPSJ 73 (2004) 2790; N. Yamamoto et al., JPSJ 82 (2013) 123701.
[5] Y. Koshikawa, H. Onodera et al., JMMM 173 (1997) 72.

intermetallics, ternary carbides, magnetic phase diagram