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Precursor effects and field-induced short-range order above the Verwey transition in single Fe3O4 crystals

机译:在单级Fe3O4晶体中verwey转型之上的前体效应和现场诱导的短程顺序

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The internal fields in single crystals of magnetite (Fe 3 O 4 ) have been previously studied through muon-spin rotation (μSR). By Maximum-Entropy (ME) μSR, we analyze Fe 3 O 4 μSR data with external fields parallel to the , or axis. The ME peak-to-noise ratio is optimized by varying the filter time and time interval. Several μSR time series indicate a beat pattern. Using MEμSR, a second frequency signal is seen at non-zero fields in the temperature range above the Verwey transition (T V = ~123 K). At zero field, MEμSR confirms with much-improved precision the existence of one frequency signal found earlier by curve fitting (CF) and Fourier transformation (FT). We compare our room temperature (RT) field-dependent MEμSR transforms for Fe 3 O 4 with those found at 205 K to study a second order phase transition at the Wigner temperature (T W = ~247 K). At RT and 205 K for fields below the demagnetization field and parallel to Fe 3 O 4 , a second MEμSR frequency is observed, missed by CF and FT. These extra magnetic fields fall on the extended magnetization curves below and above T W . At RT, a small field induces a short-range order similar to the precursor effects in the T V – T W interval. At 205 K within that precursor T-interval, we observe a comparable RT-disordered state. The existence of these additional internal fields is likely related to phonon-assisted 3d-electron(-spin) hopping and short-range order behaviors. Our MEμSR studies lead to a better understanding of the local magnetism in this Mott-Wigner glass.
机译:先前通过Muon-旋转旋转(μSR)研究了磁铁矿(Fe 3 O 4)的单个晶体中的内部场。通过最大熵(ME)μSR,我们将FE 3 O 4微观数据分析到平行于或轴的外部字段。通过改变滤波器时间和时间间隔来优化ME峰值比。几个μSR时间序列表示节拍模式。使用MEμSR,在Verwey转换的温度范围内的非零场(T V =〜123k),在非零场处看到第二频率信号。在零场处,MEμSR以曲线拟合(CF)和傅里叶变换(FT)的曲线拟合(CF)和傅立叶变换(FT)的一个频率信号的存在性大大提高了。将我们的室温(RT)现场依赖性MEμSR与在205 k处发现的那些进行比较,以研究Wigner温度(T W =〜247 k)处的二阶相转变。在退磁场下方的RT和205K处,并平行于FE 3 O 4,观察到第二MEμSR频率,由CF和FT错过。这些额外的磁场落在下方和上方的扩展磁化曲线上。在室温下,一个小场诱导类似于T V-T W间隔中的前体效应的短距离顺序。在该前体T型间隔内的205 k处,我们观察到可比的RT无序状态。这些附加的内部字段的存在可能与声子辅助3D-Electron(-Spin)跳跃和短距离顺序行为有关。我们的Meμsr研究导致对此Mott-Wigner玻璃中的局部磁性更好地了解。

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