Cluster Altered Magnetic and Transport Properties in Eu Co-Doped Ge(1-x)Mn(x)Te

TL;DR

This study investigates the magnetic and transport properties of Eu co-doped Ge(1-x)Mn(x)Te crystals, revealing ferromagnetic order, magnetoresistance effects, and anomalous Hall effect linked to magnetic clustering and electron tunneling.

Contribution

It provides new insights into how Eu co-doping influences magnetic clustering and transport phenomena in Ge(1-x)Mn(x)Te, highlighting the role of clusters in magnetic and electronic behavior.

Findings

Ferromagnetic order observed at 150-160 K.

Presence of negative and positive magnetoresistance effects.

Strong anomalous Hall effect with skew scattering mechanism.

Abstract

Magnetic and transport properties of Ge(1-x-y)Mn(x)Eu(y)Te crystals with chemical compositions 0.041 < x < 0.092 and 0.010 < y < 0.043 are studied. Ferromagnetic order is observed at 150 < T < 160 K. Aggregation of magnetic ions into clusters is found to be the source of almost constant, composition independent Curie temperatures in our samples. Magnetotransport studies show the presence of both negative (at T < 25 K) and linear positive (for 25<T <200 K) magnetoresistance effects (with amplitudes not exceeding 2%) in the studied alloy. Negative magnetoresistance detected at T < 25 K is found to be due to a tunneling of spin-polarized electrons between ferromagnetic clusters. A linear positive magnetoresistance is identified to be geometrical effect related with the presence of ferromagnetic clusters inside semiconductor matrix. The product of the polarization constant and the inter-grain exchange constant, J_P, varies between about 0.13 meV and 0.99 meV. Strong anomalous Hall effect (AHE) is observed for T < T_C with coefficients R_S independent of temperature. The scaling analysis of the AHE leads to a conclusion that this effect is due to a skew scattering mechanism.