Ferromagnetic nature in low-dimensional S = 1 antiferromagnetic Li2Ni(WO4)2 nanoparticles

We report the magnetic behaviour of ball-milled nanoparticles of antiferromagnetic spin-1 Li2Ni(WO4)2 system by magnetic susceptibility and neutron diffraction measurements. Bulk sample shows indicators of two successive three dimensional (3D) antiferromagnetic (AF) ordering at T N 1 ∼ 18 K and T N 2 ∼ 13 K in χ (T). The magnetic susceptibility and neutron diffraction measurements indicate that no long-range magnetic order is detected when bulk sample is reduced to nano size particles, despite of the identical crystal structures. The super-super exchange interaction is proposed being disrupted as a result of cell volume expansion in nanoparticles. The Zero-Field-Cooled (ZFC) and Field-Cooled (FC) curve bifurcation and M(H) curve of nanoparticle reveal that the weak ferromagnetic behavior exists at low temperature because of spin disorder on the surface of nanoparticle.