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 (Awana et al., 2010 [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 10 K at around 80, 60 and 50 kOe fields, respectively, with characteristic hysteresis shoulders along with the non-zero moment at the 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 140 kOe 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 20 kOe and decrease for 30 kOe at 15 K.

Research highlights
► Single phase SmCoAsO.
► Magnetization and heat capacity is reported.
► Interaction of Sm4f and Co3d spins in SmCoAsO.
► Successive paramagnetic (PM)–ferro-magnetic (FM)–anti-ferro-magnetic (AFM) transitions.
► Possible kinetic arrest of ferro-magnetic (FM).