EPR of Fe 3 + in a LaCaAlO 4 single crystal: Effect of substitutional disorder
EPR of Fe 3 + in a LaCaAlO 4 single crystal: Effect of substitutional disorder
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DOI：
10.1103/physrevb.67.024425
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发表时间：
2003-01
影响因子：
3.7
通讯作者：
S. Misra;S. I. Andronenko
中科院分区：
文献类型：
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作者：
S. Misra;S. I. Andronenko
在室温、液氮和液氦温度下，对掺Fe3+的LaCaAlO4单晶在X波段(9.6 GHz)进行了EPR研究，研究了钙离子和La3+离子在晶体中的同一位置位时所产生的置换无序效应。观察到的Fe3+电子顺磁共振谱线宽度随外加磁场相对于晶体c轴取向的变化与先前报道的YCaAlO4单晶中Fe3+离子的变化一致。这证实了氧化物单晶中提出的无序模型，解释了处于同一晶体位置的R3+(R表示稀土离子)和Ca2+离子的统计分布引起的线宽行为的角相关性。给出了LaCaAlO4无序在EPR谱上的具体表现。此外，利用EPR谱线位置估算了LaCaAlO4中Fe3+的自旋哈密顿参数在2 95、77和4 2K温度下的自旋哈密顿参数。利用叠加模型计算了RCaAlO4(R=Y，La)等结构晶体中的Fe3+零场分裂参数b0 2，得到了R0=1.784.0 0A时的本征参数b2(R0)=-119‘1 GHz，并用液氦温度谱确定了b0参数的绝对符号为负值.
EPR studies have been carried out on a Fe 3 + -doped LaCaAlO 4 single crystal at the X band (9.6 GHz) at room, liquid-nitrogen, and liquid-helium temperatures to study the effect of substitutional disorder that results when Ca 2 + and La 3 + ions substitute at the same site in this crystal. The variation of the observed Fe 3 + EPR linewidth as a function of the orientation of the external magnetic field with respect to the crystallographic c axis is found to be consistent with that reported previously for the Fe 3 + ion in YCaAlO 4 single crystal. This provides a confirmation of the disorder model proposed in oxide single crystals to explain the angular dependency of the linewidth behavior caused by statistical distribution of R 3 + (R denotes rare-earth ion) and Ca 2 + ions, situated in the same crystallographic position. The details of the manifestation of disorder in LaCaAlO 4 on EPR spectra have been provided. In addition, the EPR line positions have been exploited to estimate the Fe 3 + spin-Hamiltonian parameters in LaCaAlO 4 at 295, 77, and 4.2 K. The superposition model has been applied to calculate the Fe 3 + zero-field splitting parameter b 0 2 in RCaAlO 4 (R=Y, La) isostructural crystals, leading to the value of the intrinsic parameter b 2 (R 0 )=- 119′1 GHz for R 0 =1.784 A. The liquid-helium temperature spectrum has been used to determine the absolute sign of the b 0 2 parameter, which is negative.