Interplay of Sm4f and Co3d spins in SmCoAsO

We present detailed magnetization and magneto-transport studies on the title compound SmCoAsO. In a recent paper we reported [1] the complex magnetism of this compound. SmCoAsO undergoes successive paramagnetic (PM) - ferro-magnetic (FM) - anti-ferro-magnetic (AFM) transitions with decrease in temperature. This is mainly driven via the c-direction interaction of Sm4f (SmO layer) spins with adjacent (CoAs layer) ordered Co3d spins. In this article we present an evidence of kinetic arrest for FM-AFM transition. The isothermal magnetization (MH) loops for SmCoAsO exhibited the meta-magnetic transitions at 6, 8 and 10K at around 80, 60 and 50kOe fields respectively with characteristic hysteresis shoulders along with the non-zero moment at origin, thus suggesting the possibility of kinetic arrest. Suggested kinetic arrest is further evident in zero field-cooled (ZFC) and field-cooled (FC) hysteresis under high fields of up to 140kOe magnetization (MT) and the magneto-transport measurements R(T)H during FM-AFM transition. The time dependent moment experiments exhibited very small (~2-3%) increase of the same below 20kO and decrease for 30kOe at 15K.