Tricritical point and suppression of the Shastry-Sutherland phase in Ce 2(Pd 1-xNi x) 2Sn

Abstract

Structural, magnetization, and heat capacity measurements were performed on Ce 2(Pd 1-xNi x) 2Sn compounds covering the full range of the Mo 2FeB 2 structure stability (0≤x≤0.25). In this system, the two transitions observed in Ce 2Pd 2Sn (antiferromagnetic T N=4.8 K and ferromagnetic T C=2.1 K) converge into a tricritical point at T cr≈3.4 K for x cr≈0.3, where the intermediate antiferromagnetic (AF) phase is suppressed. The decrease of the T N(x) phase boundary is due to an incipient Kondo screening of the Ce-4f moments. This effect and the increase of local atomic disorder affect the formation of Ce-magnetic dimers on which the Shastry-Sutherland lattice (SSL) builds up. On the contrary, the T C(x) transition to the ferromagnetic ground state increases as a consequence of the weakening of the intermediate phase. Applied magnetic fields also suppress the AF-SSL phase as it was already observed in the stoichiometric compound. © 2012 American Physical Society.