Anomalous magnetoresistance of carbon-dopedEuB6: Possible role of nonferromagnetic regions

Influence of Pressure on the Electrical Transport Properties of Carbon-Doped EuB6

“…However, the result reported in this work is consistent with the influence of pressure on pure EuB 6 . As it was already shown in previous studies [1][2][3][4][5][6][7][8][9], the "sample dependence issue" is important in case of EuB 6 and carbon-doped EuB 6 . The reason for it is the very small number of intrinsic carriers, which influences considerably the physical properties of samples, and even very small deviations in stoichiometry or impurities can lead to a substantially different behaviour.…”

“…As it was shown by highpressure experiments [5], the FM order in EuB 6 is driven by the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. Due to a very low number of intrinsic charge carriers (≈ 10 20 cm −3 ), even small doping with carbon can drastically modify its electric and magnetic properties [6][7][8].…”

Anomalous Transport Properties of Carbon-Doped EuB6

“…Our studies have revealed that the behaviour of this system can be attributed to the effect of fluctuations in carbon concentration. According to our observations, in the bulk ferromagnetic state, carbon--rich regions give rise to helimagnetic domains that are responsible for an additional scattering term in the electrical resistivity [3][4][5]. Above the temperature of the bulk ferromagnetic ordering, T C = 4.3 K, the carbon-rich regions act as spacers that prevent magnetic polarons to link, to form ferromagnetic clusters, and eventually to percolate.…”

“…Above the temperature of the bulk ferromagnetic ordering, T C = 4.3 K, the carbon-rich regions act as spacers that prevent magnetic polarons to link, to form ferromagnetic clusters, and eventually to percolate. These spacers, being in fact volumes incompatible with the existence of magnetic polarons (and ferromagnetic state in general) are responsible for decrease in the percolation temperature and for additional (magneto)resistivity increase [4].…”

“…Not long ago we dealt with the ferromagnetic EuB 5.99 C 0.01 [3,4] exhibiting anomalously large negative magnetoresistance. Our studies have revealed that the behaviour of this system can be attributed to the effect of fluctuations in carbon concentration.…”