Charge order quenching, Griffiths phase, and magnetotransport in polycrystalline Pr_0.58Ca_0.42−ySr_yMnO₃ thin films

Abstract

We report the magneto-electrical properties of polycrystalline Pr 0.58 Ca 0.42Ày Sr y MnO 3 thin films as function of Sr doping (y). These films (thickness $300 nm) prepared by spray pyrolysis on LaAlO 3 (100) single crystalline substrates are single phase and have orthorhombic structure. The Sr free films show charge ordering (CO) transition at T CO % 240 K and the magnetic ground state has metamagnetic nature akin to the cluster glass (CG). Sr doping quenches CO and induces paramagneticferromagnetic (PM-FM) transition with a systematic destabilization of the CG state. The PM-FM transition occurs at T C % 182, 218, and 250 K for y ¼ 0.06, 0.12, and 0.22, respectively. The Sr doping induced CO quenching also gives rise to the Griffiths phase (GP) at a temperature T G > T C . The resistivity of the Sr free films shows insulating behavior typical to the CO state. An insulator-metal transition (IMT) is observed at T IM % 198 K in the y ¼ 0.06 film, which increases to 225 and 265 K at y ¼ 0.12 and 0.22, respectively. At y ¼ 0.12, the sharpest IMT that results in huge temperature coefficient of resistivity (TCR) %19%, suggests the occurrence of a bicritical state. The bicriticality is also supported by a huge low field magnetoresistance %40% at 3 kOe and colossal magnetoresistance %90% at moderate magnetic field of 10 kOe. The destabilization of the CO, the appearance of GP, and the bicritical state has been explained in terms of the phase fluctuations induced by Sr doping dependent quenched disorder.

Microstructural and magnetotransport properties of La1−xCaxMnO3 (0.45≤x≤0.60) thin films

“…We observed charge ordering in PCMO thin films on LaAlO 3 [28]. Variation of magnetotransport properties as function of Sr doping in PCMO was also found to be consistent with that of similar bulk samples [30]. Further, since the melting temperature of LaAlO 3 (∼2080 • C) the chance of chemical interaction between film and substrate is very little and therefore Al substitution in the parent compound seems improbable under used experimental conditions.…”

“…Annealing at 1000 • C does not have any chemical reaction between the film and the substrate. Recently our group has studied several manganites films, such as Pr 0.58 Ca 0.42 MnO 3 (PCMO) and Pr 0.58 Ca 0.42 − x Sr x MnO 3 (PCSMO) prepared under similar conditions [28,30]. We observed charge ordering in PCMO thin films on LaAlO 3 [28].…”

Effect of substrate and orientation on charge ordering behaviors in epitaxial Pr0.5Ca0.35Sr0.15MnO3 films

“…It has a narrow e g band and its physical properties vary greatly as the x or y changes. [17][18][19][20][21][22] Tomioka and Tokura 23 obtained the phase diagram and lattice parameters of Pr 1-x (Ca 1-y Sr y ) x MnO 3 with different x and y, which may convert from CO state to ferromagnetic metal (FM) state. From the phase diagram it is demonstrated that the bulk Pr 0.5 Ca 0.35 Sr 0.15 MnO 3 (PCSMO) is in CO state at low temperature and the T CO is about 190 K. Zhao et al 24 studied the effect of the substrate on the CO phase and transport behaviors, and showed that a large magnetic field is needed to melt CO phase if the film suffers tensile strain, indicating that tensile strain could enhance the stability of CO phase.…”