Magnetic and Transport Properties of La$_{0.7}$Sr$_{0.3}$Co$_{1-y}$Mn$_y$O$_3$

D. N. H. Nam; L. V. Bau; N. V. Khiem; L. H. Son; N. X. Phuc

paper

Magnetic and Transport Properties of La $_{0.7}$ Sr $_{0.3}$ Co $_{1 - y}$ Mn $_{y}$ O $_{3}$

arXiv:cond-mat/0207380

Abstract

While both La $_{0.7}$ Sr $_{0.3}$ MnO $_{3}$ and La $_{0.7}$ Sr $_{0.3}$ CoO $_{3}$ are ferromagnets with metallic conductivity below $T_{c}$ (360K and 220K, respectively), partial substitutions of Co by Mn in La $_{0.7}$ Sr $_{0.3}$ Co $_{1 - y}$ Mn $_{y}$ O $_{3}$ ( $y < 0.1$ ) drastically suppress the ferromagnetic long-range order pre-established by Co-O-Co double exchange and tune the conductivity towards insulating behavior. Since Mn-O-Mn double-exchange interactions are avoidable at low Mn-substitution levels, the deterioration of ferromagnetism and conductivity thus provides evidence for no Mn-O-Co double exchange (but antiferromagnetic superexchange) in the present system. At $y = 0.1$ , the ferromagnetism is no longer observed; the system becomes an insulating spin-glass with $T_{g} \approx 62$ K as estimated from the ac-susceptibility data using the conventional critical slowing-down scaling law. With further substitution ( $y \geq 0.3$ ), the ferromagnetism is recovered ( $T_{c} = 165$ K for $y = 0.3$ and 200K for $y = 0.5$ ) while the resistivity continues increasing and exhibits insulating behavior. These results indicate that the substitution is not simply a mixture of La $_{0.7}$ Sr $_{0.3}$ MnO $_{3}$ and La $_{0.7}$ Sr $_{0.3}$ CoO $_{3}$ , but produces a more complicated scenario of spin states, interactions and disorder.

RevTeX4, 5 pages, 4 figures, unpublished

Magnetic and Transport Properties of La0.7​Sr0.3​Co1−y​Mny​O3​

Abstract

Magnetic and Transport Properties of La $_{0.7}$ Sr $_{0.3}$ Co $_{1 - y}$ Mn $_{y}$ O $_{3}$