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تسجيل مستخدم جديدValence instability of cerium under pressure in the Kondo-like perovskite La$_{0.1}$Ce$_{0.4}$Sr$_{0.5}$MnO$_3$
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Effect of hydrostatic pressure and magnetic field on electrical resistance of the Kondo-like perovskite manganese oxide, La$_{0.1}$Ce$_{0.4}$Sr$_{0.5}$MnO$_3$ with a ferrimagnetic ground state, have been investigated up to 2.1 GPa and 9 T. In this compound, the Mn-moments undergo double exchange mediated ferromagnetic ordering at $T_{rm C}$ $sim$ 280 K and there is a resistance maximum, $T_{rm max}$ at about 130 K which is correlated with an antiferromagnetic ordering of {it cerium} with respect to the Mn-sublattice moments. Under pressure, the $T_{rm max}$ shifts to lower temperature at a rate of d$T_{max}$/d$P$ = -162 K/GPa and disappears at a critical pressure $P_{rm c}$ $sim$ 0.9 GPa. Further, the coefficient, $m$ of $-logT$ term due to Kondo scattering decreases linearly with increase of pressure showing an inflection point in the vicinity of $P_{rm c}$. These results suggest that {it cerium} undergoes a transition from Ce$^{3+}$ state to Ce$^{4+}$/Ce$^{3+}$ mixed valence state under pressure. In contrast to pressure effect, the applied magnetic field shifts $T_{rm max}$ to higher temperature presumably due to enhanced ferromagnetic Mn moments.
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