Enhancement of temperature coefficient of resistance (TCR) and magnetoresistance (MR) of La_0.67–xRE_xCa_0.33MnO₃ (x = 0, 0.1; RE = Gd, Nd, Sm) system via rare-earth substitution

Abstract

We investigated the influence of 10% substitution of rare-earth (RE) elements on the crystallographic, transport, and magnetic properties of La 0.67-x RE x Ca 0.33 MnO 3 (RE=Nd, Sm, and Gd, x=0.0, 0.1) manganite perovskite compounds. The bulk polycrystalline samples were synthesized using solidstate reaction method. The phase purity and crystal structure of studied samples were confirmed by room temperature X-ray diffraction followed by the Rietveld refinement analysis. A high temperature insulator to low temperature metal phase transition is observed in electrical transport measurement. We observed an enhancement in the temperature coefficient of resistance (TCR) and magnetoresistance (MR) by partially substituting La with RE ions. The maximum TCR≈22% and MR≈96% are observed in Gd doped sample. The magnetic transition temperature, T c , decreases from ∼254 K for the pristine sample to about ∼165 K for the Gd-doped sample. Our analysis of electrical and thermal transport data shows that the Small Polaron Hopping (SPH) is predominant at high temperatures conduction mechanism, whereas at low temperatures mechanism is dominated by electron-magnon scattering. The high temperature insulator paramagnetic phase to low temperature metallic ferromagnetic phase transitions are also observed in thermal conductivity and specific heat.

Polycrystalline La0.66Gd0.04Ca0.3MnO3 for magnetic-response applications: concurrent anisotropic magnetoresistance and magneto-transport under a low magnetic field

“…Interestingly, the deformation value (0.137%) of the pristine sample was close to that reported by Pal. 17 The difference between the deformation values in Table 1 corresponded to the introduction of the dopant. It can therefore be argued that trace doping with gadolinium did not lead to a substantial change in the crystal symmetry of the ceramic.…”

“…As the dopant amount rose, the peak MR ‖ and MR ⊥ values increased substantially (by 15%) until the late stage (Gd004 vs. Gd006) that was essentially flat. It should be noted that the Gd004 structure exhibited the best low-field magnetoresistance characteristics (MR ‖ = 76%, MR ⊥ = 70%), which were as large as ∼80% of those of La 0.57 Gd 0.1 Ca 0.33 MnO 3 under an ultrahigh magnetic field (9 T) 17 and ∼1.5 times higher than the values reported for La 0.6 Gd 0.1 Ca 0.3 MnO 3 in a 7 T field. 19 Recalling that the V cell () and V MnO6 () values rapidly decreased from Gd000 to Gd004, which could also be conducive to the improvement of magnetoresistance.…”

“…Regardless of the magnetization measurement mode, Gd004 shows the highest total magnetization at 100 K. A comparison of the magnetic susceptibility of the undoped and doped samples at low temperatures reveals that the pristine ceramics have a weaker FM order. The reason for this is that Gd 3+ possesses a larger magnetic moment, 17 which could be nearly spin-aligned according to the direction of the applied field. For the doping series, the maximum value of d JT (0.0412) was obtained at x = 0.04, which implied that the strongest JT distortion engendered the highest spontaneous magnetization.…”

“…In particular, the amount of dopant in the La 0.67Àx Gd x Ca 0.33 MnO 3 system up to x = 0.1 induces the replacement of Gd 3+ for La 3+ at the A-sites, which leads to a B94% MR near 150 K under an extremely large field (9 T). 17 The significant enhancement in MR also arises from the joint a Faculty of Materials Science and Engineering, Kunming University of Science and contributions of the lattice and Jahn-Teller (JT) distortions around the B-sites. Based on that, Krichene et al produced a La 0.4 Gd 0.1 Ca 0.5 MnO 3 ceramic via the conventional solid-state reaction.…”

Influence of Fe3+ ion substitution on Structural, Magnetic Properties and Magnetoresistance Effect of Pr0.75Na0.05K0.20MnO3 System

“…In order to gain more in-depth into the magnetic properties within the paramagnetic (PM) region, a graph illustrating the inverse of 𝜒𝜒𝜒𝜒 ′ plotted against temperature (T) was generated, as depicted in Figure 3 Under a 0.8 T magnetic field, however, the resistivity slightly reduced supported by the graph of log ρ versus temperature (in the inset of Figure 4), resulting in the magnetoresistance (MR) effect. The MR effect which calculated using equation MR (%) =(ρ(0,T)-ρ(H,T))/ρ(0,T) ×100% , where ρ(0,T) and ρ(H,T) represent the resistivity for 0 T and 0.8 T fields [25][26][27]. The MR % is high at low temperatures, as shown in Figure 5, indicating the extrinsic mechanism of MR effect.…”