Magnetic order and the role of inhomogeneities in Ge1−x−yPbxCryTe bulk nanocomposite crystals

We present studies of the influence of the chemical composition changes on the type of magnetic order present in bulk nanocomposite Ge1−x−yPbxCryTe crystals with the average Pb-content close to x  ≈  0.20 and Cr-content, y, varying from y  =  0.017 up to 0.043. Detailed magnetometric studies revealed the existence of two ordered magnetic states present in all our samples. All our crystals show a paramagnet to spin-glass-like state transition at temperatures from 135 K to 145 K, related to the presence of Cr5Te8 clusters in the host lattice. The second transition type depends on the Cr-content, y. In the case of samples with y equal to 0.038 and 0.043 the ferromagnetic phase is observed with TC slightly below 70 K, while in samples with lower chromium concentration the presence of spin-glass-like state slightly below 50 K is observed. The presence of clusters in our samples has significant impact on the carrier transport and magnetotransport in our samples. The presence of critical scattering on the magnetic impurities is observed in resistivity and magnetoresistance data. Nearly-linear magnetoresistance is also observed in our samples indicating a presence of strong scattering on the grain boundaries in our samples.