No Arabic abstract
We report the synthesis and characterization of a bulk diluted magnetic semiconductor (La1-xBax)(Zn1-xMnx)AsO (0 <= x <= 0.2) with a layered crystal structure identical to that of the 1111 FeAs superconductors. No ferromagnetic order occurs for (Zn,Mn) substitution in the parent compound LaZnAsO without charge doping. Together with carrier doping via (La,Ba) sub- stitution, a small amount of Mn substituting for Zn results in ferromagnetic order with TC up to ~40 K, although the system remains semiconducting. Muon spin relaxation measurements confirm the development of ferromagnetic order in the entire volume, with the relationship between the internal field and TC consistent with the trend found in (Ga,Mn)As, the 111 Li(Zn,Mn)As, and the 122 (Ba,K)(Zn,Mn)2As2 systems.
A new diluted magnetic semiconductor system, (Sr3La2O5)(Zn1-xMnx)2As2, has been synthesized and characterized. 10% Mn substitution for Zn in bulk form (Sr3La2O5)Zn2As2 results in a ferromagnetic ordering below Curie temperature, TC ~ 40 K. (Sr3La2O5)(Zn1-xMnx)2As2 has a layered crystal structure identical to that of 32522-type Fe based superconductors, and represents the fifth DMS family that has a direct counterpart among the FeAs high temperature superconductor families.
The doping effect of Sr and transition metals Mn, Fe, Co into the direct-gap semiconductor LaZnAsO has been investigated. Our results indicate that the single phase ZrCuSiAs-type tetragonal crystal structure is preserved in (La1-xSrx)(Zn1-xTMx)AsO (TM = Mn, Fe, Co) with the doping level up to x = 0.1. While the system remains semiconducting, doping with Sr and Mn results in ferromagnetic order with TC ~ 30K, and doping with Sr and Fe results in a spin glass like state below ~6K with a saturation moment of ~0.02 muB/Fe, an order of magnitude smaller than the ~0.4 muB/Mn of Sr and Mn doped samples. The same type of magnetic state is observed neither for (Zn,Fe) substitution without carrier doping, nor for Sr and Co doped specimens.
We report the synthesis and characterization of bulk form diluted magnetic semiconductors Ba(Zn1-2xMnxCox)2As2 (0 <= x <= 0.15) with a crystal structure identical to that of 122-type Fe-based superconductors. Mn and Co co-doping into the parent compound BaZn2As2 results in a ferromagnetic ordering below TC ~ 80 K. Hall effect measurements indicate that the carrier are n-type with the density of ~10^17/cm3. The common crystal structure and excellent lattice matching between the p-type ferromagnetic (Ba1-yKy)(Zn1-xMnx)2As2, the n-type ferromagnetic Ba(Zn1-2xMnxCox)2As2, the antiferrmagnetic BaMn2As2 and the superconducting Ba(Fe1-xCox)2As2 systems make it possible to make various junctions between these systems through the As layer.
We report the synthesis and characterization of bulk form diluted magnetic semiconductors I-II-V Li1.1(Zn1-xCrx)As (x = 0.03, 0.05, 0.10, 0.15)with a cubic crystal structure identical to that of III-V GaAs and II-VI zinc-blende ZnSe. With p-type carriers created by excess Li, 10% Cr substitution for Zn results in a ferromagnetic ordering below TC ~ 218 K. Li(Zn,Cr)As represents another magnetic semiconducting system with the advantage of decoupling carriers and spins, where carriers are created by adding extra Li and spins are introduced by Cr substitution for Zn.
(La1-xSrx)(Zn1-yMny)AsO is a two dimensional diluted ferromagnetic semiconductor that has the advantage of decoupled charge and spin doping. The substitution of Sr2+ for La3+ and Mn2+ for Zn2+ into the parent semiconductor LaZnAsO introduces hole carriers and spins, respectively. This advantage enables us to investigate the influence of carrier doping on the ferromagnetic ordered state through the control of Sr concentrations in (La1-xSrx)(Zn0.9Mn0.1)AsO. 10 % Sr doping results in a ferromagnetic ordering below TC ~ 30 K. Increasing Sr concentration up to 30 % heavily suppresses the Curie temperature and saturation moments. Neutron scattering measurements indicate that no structural transition occurs for (La0.9Sr0.1)(Zn0.9Mn0.1)AsO below 300 K.