Pressure response of the bimetallic chain compound MnNi(NO2)4(en)2; en = ethylenediamine
Résumé
The compound MnNi(NO2)4(en)2, en = ethylendiamine, is a rare example of a ferromagnetically coupled bimetallic chain (Jshort parallel chain not, vert, similar 2–3 K). Further, for this material, a finite inter-chain coupling triggers an antiferromagnetic (AFM) transition below TN = 2.3 K. Here, we present a susceptibility study of MnNi(NO2)4(en)2 under pressure. From our data, we derive the pressure response of the antiferromagnetic transition temperature TN. Even up to highest pressure of 8.2 kbar we find a very modest increase of TN by only not, vert, similar0.1 K. Independently, from a pressure study of the lattice parameters of MnNi(NO2)4(en)2, we calculate the bulk module of the material to not, vert, similar8.8 GPa. Combining the data TN(p) with the bulk module yields an anomalously low Grüneisen parameter Γmag of only 0.5(5). We discuss possible scenarios accounting for such a low Grüneisen parameter.