COMPETING NON-HEISENBERG INTERACTIONS IN EUXSR1-XS

The Curie-Weiss temperature theta(1)(x) of the linear susceptibility c hi(1) of the diamagnetically diluted ferromagnetic composition series EuxSr1-xS shows a pronounced x(2) term. In contrast to an earlier inte rpretation this term is explained here by ferromagnetic three-spin int eractions which exist in addition to biquadratic and bilinear exchange interactions. Biquadratic and three-spin interactions have been ident ified by means of the Curie-Weiss temperature theta(3)(x) Of the cubic susceptibility chi(3) theta(3)(x) contains one negative term proporti onal to x which is caused by antiferromagnetic biquadratic interaction s and one positive term proportional to x(2) attributed to ferromagnet ic three-spin interactions. Comparison with the theoretical expression s for theta(1) and theta(3) reveals an excellent consistency of this i nterpretation and confirms that the x(2) term in theta(3)(x) and theta (1)(x) is due to ferromagnetic three-spin interactions. These interact ions compete with antiferromagnetic biquadratic interactions as it was found in EuxSr1-xTe.