Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSpin-related magnetoresistance of n-type ZnO:Al and Zn_{1-x}Mn_{x}O:Al thin films
69
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Effects of spin-orbit coupling and s-d exchange interaction are probed by magnetoresistance measurements carried out down to 50 mK on ZnO and Zn_{1-x}Mn_{x}O with x = 3 and 7%. The films were obtained by laser ablation and doped with Al to electron concentration ~10^{20} cm^{-3}. A quantitative description of the data for ZnO:Al in terms of weak-localization theory makes it possible to determine the coupling constant lambda_{so} = (4.4 +- 0.4)*10^{-11} eVcm of the kp hamiltonian for the wurzite structure, H_{so} = lambda_{so}*c(s x k). A complex and large magnetoresistance of Zn_{1-x}Mn_{x}O:Al is interpreted in terms of the influence of the s-d spin-splitting and magnetic polaron formation on the disorder-modified electron-electron interactions. It is suggested that the proposed model explains the origin of magnetoresistance observed recently in many magnetic oxide systems.
rate research
Read More
We present the studies of electrical transport and magnetic interactions in Zn_{1-x}Mn_{x}GeAs_{2} crystals with low Mn content 0 leq x leq 0.043. We show that the ionic-acceptor defects are mainly responsible for the strong p-type conductivity of our samples. We found that the negative magnetoresistance (MR) with maximum values of about -50% is related to the weak localization phenomena. The magnetic properties of Zn1-xMnxGeAs2 samples show that the random Mn-distribution in the cation sites of the host lattice occurs only for the sample with the lowest Mn-content, x=0.003. The samples with higher Mn-content show a high level of magnetic frustration. Nonzero Curie-Weiss temperature observed in all our samples indicates that weak ferromagnetic (for x=0.003) or antiferromagnetic (for x>0.005) interactions with |{Theta}|<3 K are present in this system. The RKKY model, used to estimate the Mn-hole exchange integral Jpd for the diluted Zn/0.997/Mn/0.003/GeAs/2/ sample, makes possible to estimate the value of Jpd =(0.75+/-0.09) eV.
We have undertaken a study of diluted magnetic semiconductors $Ga_{1-x}Mn_{x}N$ and $Ga_{1-x}Cr_{x}N$ with $x=0.0625, 0.125$, using the all electron linearized augmented plane wave method (LAPW) for different configurations of Mn as well as Cr. We study four possible configurations of the impurity in the wurtzite GaN structure to predict energetically most favorable structure within the 32 atom supercell and conclude that the near-neighbor configuration has the lowest energy. We have also analyzed the ferro-magnetic as well as anti-ferromagnetic configurations of the impurity atoms. The density of states as well as bandstructure indicate half metallic state for all the systems. $T_c$ has also been estimated for the above systems.
We report the phase diagram of infinite layer Pr$_{1-x}$Sr$_{x}$NiO$_2$ thin films synthesized via topotactic reduction from the perovskite precursor phase using CaH$_2$. Based on the electrical transport properties, we find a doping-dependent superconducting dome extending between $x$ = 0.12 and 0.28, with a maximum superconducting transition temperature $T_{rm{c}}$ of 14 K at $x$ = 0.18, bounded by weakly insulating behavior on both sides. In contrast to the narrower dome observed in Nd$_{1-x}$Sr$_{x}$NiO$_2$, a local $T_{rm{c}}$ suppression near $x$ = 0.2 was not observed for the Pr$_{1-x}$Sr$_{x}$NiO$_2$ system. Normal state Hall effect measurements indicate mixed carrier contributions of both electrons and holes, and show a sign change in the Hall coefficient as functions of temperature and $x$, quite similar to that in Nd$_{1-x}$Sr$_{x}$NiO$_2$. Also similar is the observation of a minimum in the normal state resistivity associated with the superconducting compositions. These findings indicate an infinite layer nickelate phase diagram that is relatively insensitive to the rare-earth element, but suggest that disorder arising from the variations of the ionic radii on the rare-earth site affects the superconducting dome.
Resistance of Fe$_{1-x}$Ni$_x$(x=0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.9) has been measured using four probe method from 5K to 300K with and without a longitudinal magnetic field of 8T. The zero field resistivity of x=0.1 and 0.9 alloys, predominant contribution to resistivity above near room temperature is due to electron-phonon scattering, whereas for x=05 and 0.7 alloys electron-magnon scattering is dominant. Alloys with x=0.1 and 0.9 exhibit positive magnetoresistance(MR) from 5K to 300K. For x=0.5 and 0.7 alloys, magnetoresistance changes sign from positive to negative with increase in temperature. The temperature at which sign changes increase with Ni concentration in the alloy. The field dependent magnetoresistance is positive for x=0.1, 0.7 and 0.9 alloys whereas it is negative for x=0.5 alloy. MR follows linear behaviour with field for x=0.1 alloy. MR of all other alloys follow a second order polynomial in field.
The electronic transport in polypyrrole thin films synthesized chemically from the vapor phase is studied as a function of temperature as well as of electric and magnetic fields. We find distinct differences in comparison to the behavior of both polypyrrole films prepared by electrochemical growth as well as of the bulk films obtained from conventional chemical synthesis. For small electric fields F, a transition from Efros-Shklovskii variable range hopping to Arrhenius activated transport is observed at 30 K. High electric fields induce short range hopping. The characteristic hopping distance is found to be proportional to F^(-1/2). The magnetoresistance R(B) is independent of F below a critical magnetic field, above which F counteracts the magnetic field induced localization.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
