We measure transverse susceptibility (TS) in our lab using a a resonant radio frequency technique based on a tunnel diode oscillator (TDO). This method has been validated by us over the years to be an excellent probe of the dynamic magnetic response and, in particular, the anisotropy.  In this technique, a small fixed amplitude (<5 Oe) RF (10 MHz) field is applied parallel or perpendicular to to the variable external dc field and the parallel (chip) and transverse components of susceptibility can be independently resolved. Since the sample is placed in an inductive RF coil that is part of a self-resonant circuit, the shift in the resonant frequency with varying dc field and/or temperature gives a direct measure of the change in inductance and thus the sample susceptibility.

The sample is placed in a gelcap that fits in the inductive coil. The coil is part of a multifunctional probe integrated into our Physical Properties Measurement System which provides the dc field and the the variable temperature.Typical graphs of the transverse susceptibility versus magnetic field of a sample shows peaks at the switching and anisotropy fields of the sample. For thin films and structurally anisotropic materials, these peaks are highly independent of their orientation within the gelcap. How these peaks shift with field and temperature gives insight into the fundamental nature of these magnetic systems