  The dynamic magnetic susceptibility of magnetic materials near ferromagnetic
resonance (FMR) is very important in interpreting dc-voltage in electrical
detection of FMR. Based on the causality principle and the assumption that the
usual microwave absorption lineshape around FMR is Lorentzian, general forms of
dynamic susceptibility of an arbitrary sample and the corresponding dc-voltage
lineshape are obtained. Our main findings are: 1) The dynamic susceptibility is
not a Polder tensor for material with arbitrary anisotropy. Two off-diagonal
elements are not in general opposite to each other. However, the linear
response coefficient of magnetization to total rf field is a Polder tensor.
This may explain why two off-diagonal elements are always assumed to be
opposite to each other in analyses. 2) The frequency dependence of dynamic
susceptibility near FMR is fully characterized by six numbers while its field
dependence is fully characterized by seven numbers. 3) A recipe of how to
determine these numbers by standard microwave absorption measurements for an
arbitrary sample is proposed. Our results allow one to unambiguously separate
the contribution of the anisotropic magnetoresistance to dc-voltage from that
of the anomalous Hall effect. With these results, one can reliably extract the
information of spin pumping and the inverse spin Hall effect, and determine the
spin-Hall angle. 4) The field-dependence of susceptibility matrix at a fixed
frequency may have several peaks when the effective field is not monotonic of
the applied field. In contrast, the frequency-dependence of susceptibility
matrix at a fixed field has only one peak. Furthermore, in the case that
resonance frequency is not sensitive to the applied field, the field dependence
of susceptibility matrix, as well as dc-voltage, may have another non-resonance
broad peak. Thus, one should be careful in interpreting observed peaks.
