Magnetic ordering in cerium and uranium monopnictides

The most unusual feature of cerium and uranium monopnictides is the existence of very anisotropic exchange interactions which lead to a strong ferromagnetic coupling within (001) planes and an Ising-like behaviour. The ordering in uranium monopnictides has been investigated by uniaxial stress experiments which have evidenced double-k (UAs) or triple-k (USb, USb1sub(-)sub(x)Tesub(x)) structures. Studies of the magnetic properties of USb1sub(-)sub(x)Tesub(x) solid solutions have shown that a small amount of Te leads to ferromagnetism. The unusual magnetic phase diagram of CeSb and CeBi are presented and analysed within the framework of the layered Ising model. Implications of this model to uranium monopnictides are discussed. (orig.)