Positive muon spectroscopy of Nd2Fe14B and Pr2Fe14B

We have performed positive muon spin rotation measurements on polycrystalline samples of Nd₂Fe₁₄B and Pr₂Fe₁₄B in zero applied field. In both samples a single sharp μSR line was observed which was unexpected in this complicated structure. The temperature dependence of the muon frequency for Nd₂Fe₁₄B clearly reflects the spin reorientation below 150 K and can be explained qualitatively by assuming that only the c-axis component of a magnetization is sampled by the muon. A smooth decrease of the muon frequency with increasing temperature is observed for Pr₂Fe₁₄B.