ترغب بنشر مسار تعليمي؟ اضغط هنا

Magnetic, electrical and structural properties of the new Re-doped ruthenocuprate Ru1-xRexSr2GdCu2Oy

58   0   0.0 ( 0 )
 نشر من قبل Laura Teresa Corredor Boh\\'orquez
 تاريخ النشر 2014
  مجال البحث فيزياء
والبحث باللغة English
 تأليف L. T. Corredor




اسأل ChatGPT حول البحث

Despite the discovery of new superconductors classes, high-Tc oxides continue to be a current topic, because of their complex phase diagrams and doping-dependant effects (allowing one to investigate the interaction between orbitals), as well as structural properties such as lattice distortion and charge ordering, among many others. Ruthenocuprates are magnetic superconductors in which the magnetic transition temperature is much higher than the critical superconducting temperature, making them unique compounds. With the aim of investigating the dilution of the magnetic Ru sub-lattice, we proposed the synthesis of the new Ru1-xRexSr2GdCu2Oy ruthenocupratetype family, adapting the known two-step process (double perovskite + CuO)by directly doping the double perovskite, thus obtaining the new perovskite compound Sr2GdRu1-xRexOy, which represents a new synthesis process to the best of our knowledge. Our samples were structurally characterised through X-ray diffraction, and the patterns were analysed via Rietveld refinement. A complete magnetic characterisation as a function of temperature and applied field, as well as transport measurements were carried out. We discuss our results in the light of the two-lattice model for ruthenocuprates, and a relation between RuO2 (magnetic) and CuO2 (superconductor) sublattices can clearly be observed.

قيم البحث

اقرأ أيضاً

Dependence of superconducting properties of (Ca,RE)(Fe,TM)As2 [(Ca,RE)112, TM: Co, Ni)] on RE elements (RE = La-Gd) was systematically investigated. Improvement of superconducting properties by Co or Ni co-doping was observed for all (Ca,RE)112, whic h is similar to Co-co-doped (Ca,La)112 or (Ca,Pr)112. Tc of Co-co-doped samples decreased from 38 K for RE = La to 29 K for RE = Gd with decreasing ionic radii of RE3+. However, Co-co-doped (Ca,Eu)112 showed exceptionally low Tc = 21 K probably due to the co-existence of Eu3+ and Eu2+ suggested by longer interlayer distance dFe-Fe of (Ca,Eu)112 than other (Ca,RE)112.
Here we study the structural and magnetic properties of the CoFeSr2YCu2O7 compound with x = 0.0 to 1.0. X-ray diffraction patterns and simulated data obtained from Rietveld refinement of the same indicate that the iron ion replacement in CoFeSr2YCu2O 7 induces a change in crystal structure. The orthorhombic Ima2 space group structure of Co-1212 changes to tetragonal P4/mmm with increasing Fe ion. The XPS studies reveal that both Co and Fe ions are in mixed states for the former and in case of later.Although none of the studied as synthesized samples in CoFeSr2YCu2O7 are superconducting, the interesting structural changes in terms of their crystallisation space groups and the weak magnetism highlights the rich solid state chemistry of this class of materials.
Study and comparison of over 30 examples of electron doped BaFe2As2 for transition metal (TM) = Co, Ni, Cu, and (Co/Cu mixtures) have lead to an understanding that the suppression of the structural/antiferromagnetic phase transition to low enough tem perature in these compounds is a necessary condition for superconductivity, but not a sufficient one. Whereas the structural/antiferromagnetic transitions are suppressed by the number of TM dopant ions (or changes in the c-axis) the superconducting dome exists over a limited range of values of the number of electrons added by doping (or values of the {a/c} ratio). By choosing which combination of dopants are used we can change the relative positions of the upper phase lines and the superconducting dome, even to the extreme limit of suppressing the upper structural and magnetic phase transitions without the stabilization of low temperature superconducting dome.
82 - Gang Mu , Bin Zeng , Xiyu Zhu 2009
Superconductivity was achieved in PrFeAsO by partially substituting Pr^{3+} with Sr^{2+}. The electrical transport properties and structure of this new superconductor Pr_{1-x}Sr_xFeAsO at different doping levels (x = 0.05$sim$ 0.25) were investigated systematically. It was found that the lattice constants (a-axis and c-axis) increase monotonously with Sr or hole concentration. The superconducting transition temperature at about 16.3 K (95% $rho_n$) was observed around the doping level of 0.20$sim$ 0.25. A detailed investigation was carried out in the sample with doping level of x = 0.25. The domination of hole-like charge carriers in this material was confirmed by Hall effect measurements. The magnetoresistance (MR) behavior can be well described by a simple two-band model. The upper critical field of the sample with T_c = 16.3 K (x = 0.25) was estimated to be beyond 45 Tesla. Our results suggest that the hole-doped samples may have higher upper critical fields comparing to the electron-doped ones, due to the higher quasi-particle density of states at the Fermi level.
Nanocrystalline ribbons of inverse Heusler alloy Mn2Ni1.6Sn0.4 have been synthesised by melt spinning of the arc melted bulk precursor. The single phase ribbons crystallize into a cubic structure and exhibit very fine crystallite size of < 2 nm. Temp erature dependent magnetization (M-T) measurements reveal that austenite (A)-martensite (M) phase transition begins at T~248 K and finishes at T~238 K during cooling cycle and these values increase to T~267 K and T~259 K while warming. In cooling cycle, the A-phase shows ferromagnetic (FM) ordering with a Curie temperature T~267 K, while both the FM-antiferromagnetic (AFM) and M-transitions occur at T~242 K. The M-phase undergoes FM transition at T~145 K. These transitions are also confirmed by temperature dependent resistivity measurements. The observed hysteretic behaviour of magnetization and resistivity in the temperature regime spanned by the A-M transition is a manifestation of the first order phase transition. Magnetization and susceptibility data also provide unambiguous evidence in favour of spin glass . The scaling of the glass freezing temperature (Tf) with frequency, extracted from the frequency dependent AC susceptibility measurements, confirms the existence of canonical spin glass at T<145 K. The occurrence of canonical spin glass has been explained in terms of the nanostructuring modified interactions between the FM correlations in the martensitic phase and the coexisting AFM.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا