Post by Lake Shore Cosmin on Aug 1, 2018 8:14:19 GMT -5
Hello Derek, The measurement geometry can influence the quantitative results significantly, as explained before. The side mount holder is not the best choice because the sample you have can't be oriented along the applied field. The double side tape and bundling the several strips together are not going to worsen the results. The VSM was calibrated with a sphere and you measure a much larger and very different geometry sample; therefore we can say that for your particular measurement, it would have been better to first calibrate the VSM with a similar shape and size sample. Please see my comments in the previous post. The general conclusion I would like you to remain with is that the sample under test should be close in shape and dimensions to the calibration sample, otherwise the results may not be quantitatively correct.
Post by Lake Shore Cosmin on Jul 30, 2018 16:48:48 GMT -5
Hello Derek, Thank you for contacting Lake Shore about your VSM measurement! Amorphous wires and ribbons are indeed very light and measuring their mass surely poses a problem unless you have access to an analytical balance. I would still try to measure the mass precisely as much as possible but bundling together of few pieces of ribbon may work as well. The VSM is calibrated using a 3 mm diameter Ni sphere. The moment reading is correct for a similar sample size and geometry. I think you should try to stack the ribbon in a ~3 mm cube sample. If you measure an elongated sample, but you calibrate with a sphere, you should align the sample with the field in order to minimize the errors. Even when doing this, having a dramatic different sample from calibrator, can introduce errors as high as 20% in the moment reading. Since you already prepared the samples, try to glue it at the tip of the bottom-mount holder using GE varnish or superglue. Align the best you can the sample with the field direction and enlarge the EM gap to reduce the geometry mismatch effects. To further eliminate the geometry and size effects, one can create a similar shape calibrator from pure Ni material, based on precise weight measurement. The pure Ni mass magnetization is 54.94 emu/g.
Post by Lake Shore Cosmin on Apr 9, 2018 9:26:42 GMT -5
Thank you for contacting us!
The data acquisition rate is limited by the time constant which is, in this case, 0.1 s. Therefore the 7400 and 7400S can acquire 10 points per second. The field ramp rate is affected by the size of the electromagnet, electromagnet pole cap size, electromagnet gap and field range. For example, during actual measurement, on a model 7410S, at the 10mm sample access gap, one could ramp the field from -0.5T to 0.5T in one second which results in 1T/s ramp rate. In open loop though, a 10” electromagnet can be brought to >3T in less than a second, but that is not a typical mode of operation.
here you can find other specifications regarding field and electromagnet size and gaps:
Post by Lake Shore Cosmin on Aug 30, 2017 9:19:54 GMT -5
Hello, It’s great to hear that end-users are developing their own software for processing VSM data. On our side, we are doing our best to enable various experimental methods to be performed on our magnetometers. With the acquisition of the Princeton Measurements Corporation in 2012, we expanded our expertise and capabilities to rock magnetism related measurements. I do have examples of files for hysteresis, initial curve and IRM, and I will be happy to provide them to you. To do that, please e-mail me at email@example.com Thank you! Dr. Cosmin Radu Lake Shore Cryotronics
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.