Spin-glass behavior and zero-field-cooled exchange bias in a Cr-based antiperovskite compound PdNCr3

摘要

We report the synthesis, structure, and magnetic and electrical/thermal transport properties of a Cr-based antiperovskite compound PdNCr3, which crystallizes in MgCNi3-type cubic structure (space group Pm (3) over barm, No. 221). Interestingly, the spin-glass (SG) behavior, which is confirmed by the corresponding characteristic parameters (the freezing temperature T-0 = 61.4(2) K, the dynamical exponent z(nu) = 7.103(3), and the flipping time tau(0) = 2.714(2) x 10(-1)1 s), is observed in PdNCr3. Furthermore, the value of the Sommerfeld-Wilson ratio (R-W similar to 1.024(3)) for PdNCr3 is much smaller than those of cluster glass systems (R-W > 100) and Kondo cluster glass systems (R-W = 20-30), indicating that PdNCr3 is a canonical SG system. Density functional theory calculation shows that the origin of SG in PdNCr3 is attributed to the disordering located N vacancies, which is further confirmed by the measurement of sample PdN0.75Cr3 with more N deficiency. On the other hand, infrequently, the zero-field-cooled exchange bias (ZFC-EB) with an exchange bias field (HE) of about 350 Oe is observed after zero-field cooling from an unmagnetized state in PdNCr3. The values of H-E are found to depend strongly on temperature and measuring magnetic field. For PdNCr3, the ferromagnetic unidirectional anisotropy, which is the origin of our ZFC-EB effect, is formed around the ferromagnetic-SG interface isothermally during the initial magnetization process below the blocking temperature. In addition, the training effect of ZFC-EB in PdNCr3 is observed after the zero-field cooling process and has been explained well in terms of the spin configurational relaxation model.