微波合成La0.5Ba0.5CoO3中的磁致伸缩
Magnetostriction in microwave synthesized La0.5Ba0.5CoO3
AI总结：
本文研究了微波合成La0.5Ba0.5CoO3-d的磁性与磁致伸缩，发现其磁异质基态中铁磁团簇与非铁磁相共存，且反铁磁基体抑制了场致膨胀，导致磁致伸缩较小。
摘要：
通过微波辐照在20分钟处理时间内合成了单相多晶La0.5Ba0.5CoO3-d样品，并研究了其结构、磁性、电学和磁致伸缩性能。在H = 0.5 kOe场中场冷磁化强度M(T)的温度依赖性表明铁磁转变起始于TC = 177 K，零场冷与场冷M(T)之间的不可逆性即使在H = 3 kOe下仍然持续。10 K下的M(H)在最大可用场下未饱和，其值（50 kOe场下为0.87 μB/Co）远小于中间Co3+和Co4+自旋仅自旋贡献所预期的1.9 μB/Co。电阻率在低至10 K时表现出绝缘行为，仅在TC附近出现小的磁电阻（H = 70 kOe时约2%）。所有这些结果表明存在磁异质基态，弱相互作用的铁磁团簇与非铁磁相共存。样品长度沿外加磁场方向伸长（正磁致伸缩），即使在50 kOe下也未显示饱和。磁致伸缩在10 K时达到最大值（= 252 ppm），并随温度升高而减小。与La0.5Sr0.5CoO3已有数据相比，较小的磁致伸缩值表明非铁磁基体很可能是反铁磁的，它抑制了微波合成La0.5Ba0.5CoO3-d样品中铁磁团簇的场致膨胀。
英文摘要：
A single-phase polycrystalline La0.5Ba0.5CoO3-d sample was synthesized by microwave irradiation within 20 minutes of processing time and its structural, magnetic, electrical, and magnetostrictive properties were investigated. While the temperature dependence of field-cooled magnetization (M) in a field of H = 0.5 kOe indicates the onset of ferromagnetic transition at TC = 177 K, irreversibility between the zero field-cooled and field cooled M(T) persists even at H = 3 kOe. M(H) at 10 K does not saturate at the maximum available field and has a much smaller value (0.87 μB/Co in a field of 50 kOe) than 1.9 μB/Co expected for spin-only contribution from intermediate Co3+ and Co4+ spins. The resistivity shows insulating behavior down to 10 K and only a small magnetoresistance (~ 2% for H = 70 kOe) occurs around TC. All these results suggest a magnetically heterogeneous ground state with weakly interacting ferromagnetic clusters coexisting with a non-ferromagnetic phase. The length of the sample expands in the direction of the applied magnetic field (positive magnetostriction) and does not show saturation even at 50 kOe. The magnetostriction has a maximum value (= 252 ppm) at 10 K and it decreases with increasing temperature. The smaller value of magnetostriction compared to the available data on La0.5Sr0.5CoO3 suggests that non-ferromagnetic matrix is most likely antiferromagnetic and it restrains the field-induced expansion of ferromagnetic clusters in the microwave synthesized La0.5Ba0.5CoO3-d sample.
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