Precise measurements of radio-frequency magnetic susceptibility in ferromagnetic and antiferromagnetic materials

Dynafgmic magnetic susceptibility, chi, was studied in several intermetallic materials exhibiting ferromagnetic, antiferromagnetic and metamagnetic transitions. Precise measurements by using a 14 MHz tunnel diode oscillator (TDO) allow detailed insight into the field and temperature dependence of chi. In particular, local moment ferromagnets show a sharp peak in chi(T) near the Curie temperature, T-C. The peak amplitude decreases and shifts to higher temperatures with very small applied dc fields. Anisotropic measurements of CeVSb3 show that this peak is present provided the magnetic easy axis is aligned with the excitation field. In a striking contrast, small moment, itinerant ferromagnets (i.e., ZrZn2) show a broad maximum in chi(T) that responds differently to applied field. We believe that TDO measurements provide a very sensitive way to distinguish between local and itinerant moment magnetic orders. Local moment antiferromagnets do not show a peak at the Neel temperature, T-N, but only a sharp decrease of chi below T-N due to the loss of spin-disorder scattering changing the penetration depth of the ac excitation field. Furthermore, we show that the TDO is capable of detecting changes in spin order as well as metamagnetic transitions. Finally, critical scaling of chi(T,H) in the vicinity of T-C is discussed in CeVSb3 and CeAgSb2. (c) 2007 Elsevier B.V. All rights reserved.