2002/09/30 by A. Dakhama, B. Lakshmi, D. Heiman
Materials Science · Physics and Astronomy · #Condensed matter physics #Curie temperature #Electrical resistivity and conductivity #Ferromagnetism #Magnetic and transport properties of perovskites and related materials #Magnetic field #Magnetic moment #Magnetic susceptibility #Magnetism #Magnetization #Materials science #Order (exchange) #Physics #Polaron #Rare-earth and actinide compounds #Superparamagnetism #ZnO doping and properties #cond-mat.mtrl-sci
paper · pdf · doi:10.1103/physrevb.67.115204
To appear in PRB 15 Mar 2003
arxiv created 2003/02/06 · openalex publication_date 2003/03/17 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The magnetic, transport, and structural properties of (Ga,Cr)As are reported. Zincblende Ga_1\ensuremath-xCrxAs was grown by low-temperature molecular-beam epitaxy. At low concentrations, x\ensuremath∼0.1, the materials exhibit unusual magnetic properties associated with the random magnetism of the alloy. At low temperatures the magnetization M(B) increases rapidly with increasing field due to the alignment of ferromagnetic units (polarons or clusters) having large dipole moments of order 10--102\ensuremathμB. A standard model of superparamagnetism is inadequate for describing both the field and temperature dependence of the magnetization M(B,T). In order to explain M(B) at low temperatures we employ a distributed magnetic-moment model in which polarons or clusters of ions have a distribution of moments. It is also found that the magnetic susceptibility increases for decreasing temperature but saturates below T=4K. The inverse susceptibility follows a linear-T Curie-Weiss law and extrapolates to a magnetic transition temperature \ensuremathθ=10K. In magnetotransport measurements, a room-temperature resistivity of \ensuremathρ=0.1\ensuremathΩcm and a hole concentration of \ensuremath∼1020cm^\ensuremath-3 are found, indicating that Cr can also act as an acceptor similar to Mn. The resistivity increases rapidly for decreasing temperature below room temperature, and becomes strongly insulating at low temperatures. The conductivity follows exp[\ensuremath-(T1/T)1/2] over a large range of conductivity, possible evidence of tunneling between polarons or clusters.