Finite sample size effects on the calibration of vibrating sample magnetometer
Finite sample size effects on the calibration of vibrating sample magnetometer
复制标题
有限样品尺寸对振动样品磁力计校准的影响
DOI：
10.1109/20.951296
复制
发表时间：
2001
影响因子：
2.1
通讯作者：
B. Dodrill
中科院分区：
文献类型：
--
作者：
J. Lindemuth;J. Krause;B. Dodrill
校准 VSM 力矩读数的正常程序是使用已知磁矩的 Ni 球来确定由锁定放大器测量的 VSM 传感线圈的力矩/电压。经常做出的假设是，当将未知样本放入 VSM 中时，将产生相同的力矩/伏特。这个假设应该仔细检查。如果样品是薄膜并且与镍球的尺寸相比较大，则测量中可能会引入高达 15% 的系统误差。这些系统误差由样品几何形状引起，可以通过用与待测样品尺寸和形状相同的镍薄膜替换用于校准的镍球来校正。来自均匀磁化球体的场是偶极场。大直径薄膜不能近似为点偶极子。在本文中，使用薄膜的近似值来计算 VSM 线圈中感应的信号。近似是将薄膜视为扁球体。这种近似的优点是样品可以被均匀磁化，并且外场的解可以简单地用扁球谐波表示。
The normal procedure for calibration of the moment readings of a VSM is to use a Ni sphere of known magnetic moment to determine the moment/volt of the VSM sensing coils as measured by a lockin amplifier. The often made assumption is that when an unknown sample is placed in the VSM the same moment/volt will be produced. This assumption should be carefully checked. If the sample is a thin film and is large compared to the size of the Ni sphere, systematic errors as large as 15% can be introduced into the measurement. These systematic errors arise from the sample geometry and can be corrected by replacing the Ni sphere used for calibration with Ni thin films the same size and shape as the sample to be measured. The field from a uniform magnetized sphere is a dipole field. Large diameter thin films cannot be approximated as point dipoles. In this paper an approximation for a thin film is used to calculate the signal induced in the VSM coils. The approximation is to treat the thin film as an oblate spheroid. This approximation has the advantage that the sample can be uniformly magnetized and solutions for the external field can be simply expressed in oblate spheroidal harmonics.