Co掺杂钙钛矿锰氧化物La0.8Sr0.2MnO3电磁特性研究

采用传统的高温固相反应法制备了La_0.8Sr_0.2Mn_1-xCo_xO₃(x = 0, 0.1, 0.3)多晶样品。系统研究了Co掺杂量对La_0.8Sr_0.2MnO₃(LSMO)多晶样品的类Griffiths相、磁熵变、临界行为和电输运性质的影响。研究结果表明: 制备的多晶样品均具有菱形对称结构; 三样品在低温磁转变温度(T_C2)以上均存在类Griffiths相; La_0.8Sr_0.2Mn_1-xCo_xO₃(x = 0, 0.1, 0.3)样品外加磁场为7 T的最大磁熵变ΔS_max分别为-2.28、-2.05和-2.75 J/(kg·K), Co元素的掺杂使得ΔS_max先减小后增大; 母相的临界行为与平均场模型拟合得最好, 掺杂后样品的临界行为和3D海森伯模型拟合最好; 母相为半导体材料, Co元素掺杂量达到0.1时在低温磁转变温度(T_C2)附近出现金属绝缘体转变; 高温区三样品的导电方式均满足小极化子模型。

Electromagnetic Property of Co-doped La0.8Sr0.2MnO3 Perovskite Manganese Oxides

La_0.8Sr_0.2Mn_1-xCo_xO₃ (x = 0, 0.1, 0.3) samples were prepared via the conventional high-temperature solid-state reaction method. The effects of Co doping on Griffiths phase, magnetic entropy change, critical behavior, and electrical transport properties of La_0.8Sr_0.2MnO₃ (LSMO) polycrystalline samples were systematically investigated. Results show that the prepared polycrystalline samples all have rhombohedral symmetry structures with Griffiths phase above the low temperature magnetic transition temperature (T_C2). When magnetic field is applied to the La_0.8Sr_0.2Mn_1-xCo_xO₃ (x = 0, 0.1, 0.3) samples, the maximum magnetic entropy change ΔS_max for 7 T is -2.88, -2.05, and -2.75 J/(kg·K), respectively. Doping of Co element makes ΔS_max decrease first and then increase. The critical behavior of the parent phase fits best with the mean field model, and that of the sample after doping fits best with the 3D Heisenberg model. The mother phase is a semiconductor material, and the metal insulator transition appears near the low temperature magnetic transition temperature (T_C2) when the Co element doping amount reaches 0.1. The conductivity of the three samples in high temperature region satisfies the small polaron model.