Low‐field magnetic behavior of LaMn 2– x Ni x Si 2 silicides

We have performed X‐ray diffraction (XRD) and AC magnetic susceptibility measurements on polycrystalline LaMn 2– x Ni x Si 2 (0.0 ≤ x ≤ 2.0) silicides for magnetic characterization in fields of about a few Oe at a temperature range 15–325 K. All compounds crystallize in the naturally layered ThCr 2 Si 2 ‐type structure with the space group I 4/ mmm . Substitution of Ni for Mn leads to a linear decrease in the lattice constant c and the unit cell volume, while it gives rise to a change of magnetic properties from ferromagnetic to anti‐ferromagnetic behavior for small values of x < 1. The sample with x = 0.8 has a Néel temperature of about 35 K, associated with anti‐ferromagnetic behavior. However, for x = 1, anti‐ferromagnetic behavior is diminished and paramagnetic behavior becomes dominant. For x = 2, the sample becomes virtually non‐magnetic. The samples with x ≤ 0.5 exhibit mixed magnetic properties composed of ferromagnetic and anti‐ferromagnetic interactions, below the Curie temperature T C (Mn). The results are collected in the magnetic phase diagram. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)