Post by Professor Lake Shore on Jan 31, 2017 17:51:19 GMT -5
Is saddling (centering) the sample important for a magnetometer, especially with a VSM?
Yes, because the position of the sample will directly affect the detection efficiency and, in turn, the accuracy of the moment values. If you don’t saddle it by positioning the sample at the center of the detection, the moment value will be incorrect. Your measurement will be only qualitative not quantitative – that is, you see the shape, but you cannot rely on the numbers of the measurement. For more guidance on this, see Section 4.3.3. in the 7400-S Series VSM user manual, which shows moment vs. position on all three (X-Y-Z) axes. It explains how much moment is affected by a sample being off-center.
Post by Lake Shore Cosmin on Mar 6, 2017 10:01:38 GMT -5
If the sample or some part of it is ferromagnetic, and if the approximate saturation field is known, we should apply a field equal with the saturation field or larger. Since the field applied during moment gain calibration is 5000 Oe, it became the norm to just use this value to saddle most of the samples. The samples with significant diamagnetic contribution, such as a very thin ferromagnetic film on glass substrate, may benefit from applying a lower field, for example 1000 Oe, in order to avoid the moment being too low. In such special cases, it may be beneficial to only saddle visually, run a quick hysteresis measurement, and only afterwards choose a suitable saddling field. In any case, I recommend trying first to saddle with a 5000 Oe field.