Emergence of Magnetic States in Pr2Fe4–xCoxSb5 (1 x < 2.5)

Single crystals of Pr2Fe4–xCoxSb5 (1 x 2Fe4Sb5 structure type (I4/mmm). The structure of Pr2Fe4–xCoxSb5 (1 x x ∼ 1 analogue is metallic and exhibits a magnetic transition at T1 ≈ 25 K. The magnetic moment obtained from the Curie–Weiss fit is 11.49(4) μB, which is larger than the spin-only Pr3+ moment. The x ∼ 2 analogue orders magnetically at T1 ≈ 80 and T2 ≈ 45 K. This is the first case of the substitution of Co into the La2Fe4Sb5 structure type, evidenced by the increased concentration of dopant with decreased lattice parameters coupled with a change in the transition temperature with a change in the cobalt concentration. The added complexity in the magnetic behavior of the x ∼ 1 and 2 analogues indicates that the increased concentration of Co invokes an additional magnetic contribution of the transition metal in the sublattice. Furthermore, X-ray photoelectron spectroscopy measurements support the change in the oxidation states of transition metals with increasing cobalt concentration.