AI 中文总结
研究对比微波辐照与传统加热合成的LaMnO3样品在0.9 - 3 GHz的高频磁电阻，发现室温结构及磁性不同，CH-LMO高频电阻随磁场降，MW-LMO有峰值且与频率有关，将其归因于顺磁态自旋电流驱动共振激发，强调需最佳空穴密度。
AI 中文摘要
与众多直流磁电阻研究相比，空穴掺杂的LaMnO3在几MHz以上频率的磁电阻鲜有报道。本文对比了在微波炉中通过微波辐照氧化物前驱体合成的多晶LaMnO3（MW-LMO）和在电炉中通过传统加热合成的（CH-LMO）在f = 0.9 - 3 GHz频率范围内的高频磁电阻。室温结构不同，磁性和电阻研究表明CH-LMO在140 K以下是倾斜反铁磁绝缘体，MW-LMO是铁磁金属。CH-LMO高频电阻随直流磁场增强逐渐降低，MW-LMO在f≥1.4 GHz时在H = Hr出现峰值且Hr随f线性增加。将MW-LMO高频磁电阻特性归因于顺磁态自旋的电流驱动共振激发，CH-LMO未出现此现象凸显观察此效应需最佳空穴密度。
英文摘要
Magnetoresistance of hole-doped LaMnO3 at frequencies above a few MHz has been seldom reported compared to numerous studies on magnetoresistance measured at direct current. Here, we contrast the high-frequency magnetoresistance in the frequency range f = 0.9-3 GHz in polycrystalline LaMnO3 (LMO) synthesized by microwave irradiation of oxide precursors in a microwave furnace (MW-LMO) and by conventional heating (CH-LMO) in an electrical furnace. The structure at room temperature changed from orthorhombic in CH-LMO to rhombohedral in MW-LMO. A combination of magnetization and resistivity studies suggest that the CH-LMO sample is a canted antiferromagnetic insulator below 140 K but the MW-LMO is a ferromagnetic metal with T_C = 240 K. While the high-frequency resistance of the CH-LMO sample at 300 K decreases gradually with increasing strength of the applied dc magnetic field for all f, a peak appears at H = H_r larger than 0 gauss when f equal or greater than 1.4 GHz in the MW-LMO sample and H_r increases linearly with f. We attribute the observed features in the high-frequency magnetoresistance of MW-LMO to current-driven resonant excitation of spins in the paramagnetic state. Its absence in the CH-LMO sample highlights the need for an optimum hole density to observe this effect.
Comments18 pages, 6 figures
