Presence of a Spin Glass State in Antiferromagnetic Tb₂CuIn₃

Abstract:

Evidence of the coexistence of an ordered antiferromagnetic and a spin glass state is given by studying a polycrystalline Tb₂CuIn₃ sample with neutron diffraction in a non-magnetic and a magnetic environment. Tb₂CuIn₃ is an antiferromagnet with competing exchange interactions (J₁> 0 for nearest neighbours and J₂ < 0 for next nearest neighbours) and an ordering temperature T_N =33 ± 1 K. Powder diffraction measurements reveal a broad diffuse peak - due to short-range magnetic order - underneath the (100) long-range order magnetic Bragg reflection. The exposure of the sample in magnetic fields up to 7.5 T, under both zero field and field-cooled conditions, show that neither the long-range magnetic order nor the short-range order are destroyed by the outer magnetic fields. The almost field independent behaviour of the magnetic intensities is explained by the existence of a spin glass state. Support on the simultaneous presence of antiferromagnetic and spin glass states is given by recent ac-dc magnetic measurements. The infinite range model for spin glasses with strong uniaxial anisotropy has predicted this kind of magnetic behaviour.