Magnetization and spin-flip Raman scattering in Cd1−xCrxSe and Cd1−xVxSe

X. Lu, I. Miotkowski, S. Rodriguez, A. K. Ramdas, H. Alawadhi, T. M. Pekarek
2012 Physical Review B  
Spin-flip Raman scattering (SFRS) from donor-bound electrons in II-VI diluted magnetic semiconductors containing 3d transition-metal ions, e.g., Cd1−xCrxSe and Cd1−xVxSe, allows one to explore the exchange interaction between the conduction band or donor electrons with the 3d magnetic ions, so called s-d exchange interaction. The s-d exchange energy, being the SFRS Raman shift after subtracting the intrinsic Zeeman splitting characterized by g*=0.52 for CdSe, together with the magnetization
more » ... urements of those DMSs, allow one to deduce the s-d exchange constant N0α. For Cd1−xCrxSe and Cd1−xVxSe, the N0α values are 210 ± 13 meV and 269 ± 10 meV, respectively. PACS numbers: I. INTRODUCTION II-VI semiconductors in which 3d-transition metal ions (3d-TMIs)are incorporated resulting in a diluted magnetic semiconductors (II-VI DMSs) have been the focus of intense research thanks to the coexistence of semiconductor and magnetic phenomena, resulting from the so-called"sp-d" exchange interaction between the band carriers and localized electrons of the magnetic ions 1 . Theoretical investigations 2,3 predict that the p-d exchange interaction in II-VI DMSs with 3d transition-metal ions (TMIs) having less than a half-filled 3d shell (e.g., Sc, Ti, V and Cr) are ferromagnetic, in striking contrast to the antiferromagnetic character of those having a half-filled (e.g., Mn) or more than a half-filled (e.g., Co, Fe,Ni and Cu) 3d shell. This ferromagetic p-d exchange interaction has been confirmed experimentally in several Cr-based DMSs 4-7 on the basis of magneto-reflectivity measurements. Mac et al. 8 also report a ferromagnetic p-d exchange interaction in Cd 1−x V x S as deduced from the Zeeman effect of the excitonic reflectivity and luminescence. The distinct varieties of magnetism displayed by TMIs continue to provide a strong motivation for synthesizing and studying such DMSs. The magnetism displayed by a given TMI is intimately related to its localized magnetic moment influenced by its internal electronic level structure as a constituent of the non-magnetic host lattice. As a result, Mn-and Co-based DMSs show paramagnetism which follow B 5/2 and B 3/2 Brillouin functions, respectively 1,9 ; Fe-based DMSs, however, exhibit the van Vleck-type paramagnetism. 9-11 V-based DMSs, e.g., Cd 1−x V x T e, the magnetization follows a B 3/2 Brillouin function. However, Cr-based DMSs display a paramagnetism 4,12-15 that is intermediate between Brillouin-type and van Vleck-type. In V-and Cr-based DMSs, the ferromagnetic s,p-d exchange interaction may also mediate the ferromagnetic coupling between the magnetic ions via d-d exchange interaction. Indeed room-temperature ferromagnetism of Zn 1−x Cr x T e film with x=0.2 has been reported 16,17 , and has received notice in connection with potential spintronic 18 applications. Due to the small concentrations in which V and Cr can be incorporated in DMSs, with correspondingly small excitonic Zeeman splittings, not all the excitonic Zeeman lines are resolved in magneto-reflectivity measurements. As a result, the sp-d exchange interaction constants N 0 α and N 0 β cannot be deduced separately in those measurements
doi:10.1103/physrevb.86.115213 fatcat:4wpsmfsssbfy3klouf7t7elzii