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تسجيل مستخدم جديدSuppression of the Shastry-Sutherland phase in Ce$_{2}$Pd$_{2}$Sn at a field induced critical point
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The magnetic phase diagram of Ce$_2$Pd$_2$Sn is investigated through the field dependence of thermal, transport and magnetic measurements performed at low temperature. The upper transition, $T_M=4.8$ K is practically not affected by magnetic field up to B=1 T, whereas the lower one $T_C(B)$ rapidly increases from 2.1 K joining $T_M$ in a critical point at $T_{cr}=(4.2pm 0.3$)K for $B_{cr}=(0.12pm 0.03)$ T. At that point the intermediate phase, previously described as an unstable Shastry-Sutherland phase, is suppressed. A detailed analysis around the critical point reveals a structure in the maximum of the $partial M/partial B(B)$ derivative which could be related to the formation of a novel phase in that critical region.
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Structural, magnetization and heat capacity measurements were performed on Ce$_2$(Pd$_{1-x}$Ni$_x$)$_2$Sn ($0 leq x leq 0.25$) alloys, covering the full range of the Mo$_2$FeB$_2$ structure stability. In this system, the two transitions observed in C
e$_2$Pd$_2$Sn (at $T_N=4.8$,K and $T_C=2.1$,K respectively) converge into a tri-critical point at $T_{cr}approx 3.4$,K for $xapprox 0.3$, where the intermediate antiferromagnetic AF phase is suppressed. The $T_N(x)$ phase boundary decrease is due to an incipient Kondo screening of the Ce-4f moments and local atomic disorder in the alloy. Both mechanisms 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 AF-SSL phase. Applied magnetic field also suppresses the AF phase like in the stoichiometric compound.
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