Tricritical point and suppression of the Shastry-Sutherland phase in Ce2(Pd1-xNix)2Sn

Structural, magnetization and heat capacity measurements were performed on Ce2(Pd1-xNix)2Sn compounds covering the full range of the Mo2FeB2 structure stability (0 x 0.25). In this system, the two transitions observed in Ce2Pd2Sn (antiferromagnetic TN=4.8 K and ferromagnetic TC=2.1 K) converge into a tri-critical point at Tcr 3.4 K for xcr 0.3, where the intermediate antiferromagnetic AF phase is suppressed. The decrease of the TN(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 TC(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