Shubnikov-de Haas (SdH) effect and magnetoresistance measurements of single crystals of diluted II-V magnetic semiconductors (Cd Zn Mn )As (x + y = 0.4, y = 0.04 and 0.08) are investigated in the temperature range T = 4.2 ÷ 300 K and in transverse magnetic field B = 0 ÷ 25 T. The values of the cyclotron mass m , the effective g-factor g*, and the Dingle temperature T are defined. In one of the samples (y = 0.04) a strong dependence of the cyclotron mass on the magnetic field m (B) = m(0) + αB is observed. The value of a phase shift close to β = 0.5 indicates the presence of Berry phase and 3D Dirac fermions in a single crystals of (Cd Zn Mn )As in one of the samples (y = 0.08).
Orientation dependences of magnetoresistance, ρB À Á , of single crystal (Cd 0.6 Zn 0.36 Mn 0.04 ) 3 As 2 having tetragonal P4 2 /nmc symmetry have been studied. Three orientations between electrical current,J, flowing along crystal (100) plane and magnetic field,B, have been used as follows: 1)B is perpendicular to bothJ and (100) plane; 2)B is perpendicular toJ but parallel to (100) plane; 3)B is parallel to bothJ and (100) plane. Asymmetry in curves ρB À Á is observed for all orientations. For orientation (2), crossover from negative to positive magnetoresistance is found as magnetic field changes its direction from one position corresponding to negativeB to opposite direction corresponding to positiveB. So magnetoresistance parity typical for numerous solids is violated for this orientation. The Shubnikov-de Haas (SdH) oscillations are observed for all orientations above %1.8 T and below %40 K. The effective mass of electrons extracted from SdH oscillations analysis is found to be orientation dependent. Smeared kinks correlated with the SdH oscillations are also observed in the Hall effect study for orientation (1). Magnetoresistance peculiarities can be related to specific properties of the Dirac semimetals and their evolution under magnetic field.Magnetoresistance, ρB À Á , characterizing a change of the electrical resistivity, ρ, of solid in applied magnetic field,B, is
Charge carriers parameters on a 2D-layer surface for (Cd 1−x−y Zn x Mn y ) 3 As 2 (y=0.08) (the concentration n D 2 =1.9×10 12 cm -2 , the effective value of the 2D-layer = d n n
Features in the transverse magnetoresistance of single-crystalline diluted magnetic semiconductors of a (Cd1–x–yZnxMny)3As2 system with x + y = 0.3 have been found and analyzed in detail. Two groups of samples have been examined. The samples of the first group were thermally annealed for a long time, whereas the samples of the second group were not thermally annealed. The Shubnikov–de Haas (SdH) oscillations were observed for both groups of the samples within a 4.2 ÷ 30 K temperature range and under transverse magnetic field sweeping from 0 up to 11 T. The value of a phase shift, according to the SdH oscillations, was found to be a characteristic of the Berry phase existing in all the samples, except the unannealed sample with y = 0.08. Thickness of 2D surface topological nanolayers for all the samples was estimated. The thickness substantially depended on Mn concentration. The experimental dependence of reduced cyclotron mass on the Fermi wave vector, extracted from the SdH oscillations for the samples with different doping levels, is in satisfactory agreement with the predicted theoretical linear dependence. The existence of the Dirac fermions in all the samples studied (except the unannealed sample with y = 0.08) can be concluded from this result.
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