Experimental and computational study of the magnetic properties of ZrMn2-xCoxGe4O12

Polycrystalline samples in the solid solution ZrMn2−xCoxGe4O12 (x = 0.0, 0.5, 1.0, 1.5 and 2.0) have been prepared using the ceramic method and characterised by a combination of magnetometry, X-ray diffraction and neutron diffraction. They all adopt the space group P4/nbm with a ∼ 9.60, c ∼ 4.82 A and show long-range magnetic order with transition temperatures, TC, in the range 2 ≤ TC/K ≤ 10. The underlying magnetic structure is the same in each case but the ordered spins lie along [001] when x = 0.0 and in the (001) plane for all other compositions. In all cases the magnetically-ordered phase is a weak ferromagnet although the magnitude of the spontaneous magnetisation and the strength of the coercive field are composition-dependent. The magnetic structure can be rationalized by considering the strengths of the interactions along the distinct M–O–Ge–O–M superexchange pathways in the crystal and the observed magnetic structure is entirely consistent with the predictions of ab initio calculations.