Hi Andrew,
I don't see anything illigal with the material definition. I am surprised with permeability much less than 1, but with non-zero MS value, the permeability is overridden with the Ferrite Permeability Tensor based on Polder model. Search "Ferrite Permeability Tensor" in on-line HFSS Help for detailed formulas. Magnetic Bias source as shown is set to be along Z axis.
Note that when you plot H-field in HFSS, you don't plot DC external field but RF H-field. HFSS solves for E-field (as complex vector) and then deribes H-field based on Maxwell eqs. and solved E-field.
If you still think that RF H-field is too small, see that the power is actually entering the design. How S-parameters look like? Can you plot E-field? Is it as expected?
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