Hello, I'm running a 3D magnetostatic simulation that models portions of floppy disk material stacked up to create regions of different thicknesses (geometry screenshot attached). This is being used as a validation simulation for other geometries we want to simulate.
The total assembly is about 1 inch by 0.5 inch. There are three groups of 3 concentric rings in between two of these floppy stacks so that I can obtain field results in regions where water tubes were in the original experiment.
The issue I'm having is that the resultant fields are much greater than we saw empirically in our experiment. For the 3 different regions, we saw line widths (from the gyromagnetic ratio of a proton) on the order of Hz for individual regions and peak spacing of about 2kHz between regions. When I create a Normal B Field Histogram and use the gyromagnetic ratio of a proton I get about 20kHz spacing and 15kHz linewidths. So we are getting much larger fields in the simulation than what we were observing in the experiment.
Everything runs great as far as meshing and convergence goes. Right now I'm using "Magnetic Fields, No Currents" for physics and a custom material for the floppy material. It runs in under 1 minute at fine mesh level.
I custom defined the material using data from 2 magnetization curves I found in published papers, both agreeing very closely in their values although only providing data up to 0.5T. I converted those curves to a BH curve up to 7T by log fitting the magnetization curve to a point where the derivative is practically 0 and then defining an analytic BH curve for the material using the linear portion of that magnetization curve. Specifically, I took the max value for the magnetization, and then defined the analytic equation as B = u0*(H+Mmax) from the relation B=u0(H+M) since 7T is way past saturation for the material and it will then behave linear.
We are going to test our floppy samples with a SQUID at 7T this week, but besides that, are there any other issues that could be going on in COMSOL with modeling a thin-film?
Thank you.
The total assembly is about 1 inch by 0.5 inch. There are three groups of 3 concentric rings in between two of these floppy stacks so that I can obtain field results in regions where water tubes were in the original experiment.
The issue I'm having is that the resultant fields are much greater than we saw empirically in our experiment. For the 3 different regions, we saw line widths (from the gyromagnetic ratio of a proton) on the order of Hz for individual regions and peak spacing of about 2kHz between regions. When I create a Normal B Field Histogram and use the gyromagnetic ratio of a proton I get about 20kHz spacing and 15kHz linewidths. So we are getting much larger fields in the simulation than what we were observing in the experiment.
Everything runs great as far as meshing and convergence goes. Right now I'm using "Magnetic Fields, No Currents" for physics and a custom material for the floppy material. It runs in under 1 minute at fine mesh level.
I custom defined the material using data from 2 magnetization curves I found in published papers, both agreeing very closely in their values although only providing data up to 0.5T. I converted those curves to a BH curve up to 7T by log fitting the magnetization curve to a point where the derivative is practically 0 and then defining an analytic BH curve for the material using the linear portion of that magnetization curve. Specifically, I took the max value for the magnetization, and then defined the analytic equation as B = u0*(H+Mmax) from the relation B=u0(H+M) since 7T is way past saturation for the material and it will then behave linear.
We are going to test our floppy samples with a SQUID at 7T this week, but besides that, are there any other issues that could be going on in COMSOL with modeling a thin-film?
Thank you.