Fermi surface magnetization of Fe-doped NbSb$_2$ investigated by magnetic quantum oscillations

Magnetic quantum oscillations (MQOs) have been widely used as a tool for probing Fermi surfaces. The shape and topology of the Fermi surface and the related physical parameters, such as the cyclotron mass and relaxation time, can be verified by carefully analyzing the frequency, amplitude, and phase of MQOs. In particular, phase analysis, from which we can obtain the Berry phase, has received much attention with the growing interest in the topology of condensed matter physics. Here, beyond the conventional uses of MQOs, we show that MQOs can be used to determine the Fermi surface magnetization. We doped dilute magnetic element Fe into the Dirac semimetal NbSb$_2$ to only introduce magnetism without changing the shape of the Fermi surface. We observed a phase shift in magnetically doped Fe-NbSb$_2$, which is in contrast to the lack of a phase shift in pristine NbSb$_2$ and nonmagnetic Bi-doped NbSb$_2$, indicating the strong exchange interaction between doped magnetic impurities and Fermi surface electrons. We estimated the Fermi surface magnetization introduced by magnetic Fe doping from the phase shift. This work demonstrates not only how tiny magnetic impurities can significantly change the Fermi surface magnetization but also how the Fermi surface magnetization can be investigated by phase analysis of MQOs.