Effects of Zr substitution on structural,morphological,and magnetic properties of bismuth iron oxide phases

The present study involves co-precipitation method to grow un-doped and Zr-doped bismuth iron oxide with x_（Zr）=0.10–0.30. The molar solutions of ferric chloride（FeCl_3）, zirconyle chloride（ZrOCl_2）, and bismuth chloride（BiCl_3） are prepared in distilled water, and are allowed to react with sodium hydroxide（Na OH）. The synthesized powders are then converted into pellets, which are sintered at 500℃ for two hours in a muffle furnace. X-ray diffraction（XRD） shows multi-phase formation in un-doped and Zr doped samples. Scanning electron microscope（SEM） depicts layered structure at low Zr concentration x_（Zr）= 0.10, while uniform surface with smaller grains and voids is observed at x_（Zr）= 0.20, but at x_（Zr）= 0.30, cracks and voids become prominent. The ferromagnetic nature of the un-doped sample is observed by vibrating sample magnetometer（VSM）, while paramagnetic behavior appears due to Zr doping. The ferromagnetism in un-doped sample is lost by Zr doping, which is due to the formation of additional Fe–O–Zr bonds that induce paramagnetic behavior.

Theoretical investigation of optical properties and band gap engineering for Zn1-xTMxTe(TM=Fe,Co)alloys by modified Becke-Johnson potential

The direct band gap ZnTe with transition metal （TM） impurities plays a vital role in optoelectronic and spintronic applications. In the present study, we use the advanced modified Becke-Johnson （mBJ） functional for performing the structural computations and detailed investigations of the optical characters in Zn1_xTMxTe （TM = Fe, Co） alloys with 0 ≤ x ≤1. By employing the FP-LAPW method, we determine various optical parameters for the ternary alloys and for the end binaries. The calculated static dielectric constants and optical band gaps for Zn1_xTMxTe （TM = Fe, Co） have an inverse relation that verifies the Penn model. We find that the static dielectric constant is nearly equal to the square of the static refractive index, and both increase with TM content. Furthermore, we also find a slight shift of peaks to a higher energy region with increasing TM concentration. The decreasing band gap and high value of the absorption in the visible region of electromagnetic spectrum make these alloys suitable for photonic and solar cell applications.

Study of magnetic and optical properties of Zn1-xTMxTe(TM = Mn,Fe,Co,Ni) diluted magnetic semiconductors：First principle approach

We present structural,magnetic and optical characteristics of Zn_（1-x）TM_xTe（TM = Mn,Fe,Co,Ni and x = 6.25%）,calculated through Wien2 k code,by using full potential linearized augmented plane wave（FP-LAPW） technique.The optimization of the crystal structures have been done to compare the ferromagnetic（FM） and antiferromagnetic（AFM） ground state energies,to elucidate the ferromagnetic phase stability,which further has been verified through the formation and cohesive energies.Moreover,the estimated Curie temperatures T_c have demonstrated above room temperature ferromagnetism（RTFM） in Zn_（1-x）TM_xTe（TM =Mn,Fe,Co,Ni and x= 6.25%）.The calculated electronic properties have depicted that Mn- and Co-doped ZnTe behave as ferromagnetic semiconductors,while half-metallic ferromagnetic behaviors are observed in Fe- and Ni-doped ZnTe.The presence of ferromagnetism is also demonstrated to be due to both the p-d and s-d hybridizations between the host lattice cations and TM impurities.The calculated band gaps and static real dielectric constants have been observed to vary according to Penn＇s model.The evaluated band gaps lie in near visible and ultraviolet regions,which make these materials suitable for various important device applications in optoelectronic and spintronic.