Anisotropic behaviour in the magnetic field dependence of the low temperature electrical resistance of calcium-doped lanthanum manganate thin films grown by RF magnetron sputtering

Magnetic tunnel junctions (MTJs) based on fully spin polarized ferromagnetic manganites have generated a lot of interest due to their enhanced field sensitivity at low temperatures. However, the tunneling magnetoresistance (TMR) drops rapidly with increasing temperature due to the reduction of spin polarization at the manganite-insulator interface. We have devised a method for creating intrinsic tunnel barriers by tuning the phase competition in manganites using substrate induced strain. Ultrathin films (7.5nm) of the mixed phase manganite (La0.5Pr0.5)0.67Ca0.33MnO3 (LPCMO) grown on the substrate (110) NdGaO3 using pulsed laser deposition show positive magnetoresistance (MR) of about 30% at magnetic fields less than 1T. Unlike the fabricated MTJ devices, this MR effect has its maximum value close to the insulator to metal transition temperature and reduces with decreasing temperature. To find out the mechanism leading to this positive MR, the effect of three orientations of the magnetic field on the LPCMO thin films were studied: (1) perpendicular to the plane of the film, (2) parallel to the plane of the film and applied current, and (3) parallel to the plane of the film but perpendicular to the applied current. The effect of field orientation suggests that a possible mechanism for the positive MR is tunneling magnetoresistance due to the spin conserving tunneling process across the insulating regions separating the ferromagnetic metallic regions. The voltage dependence of the MR also supports this mechanism. Our results suggest a novel method for obtaining enhanced TMR in manganite based MTJs by creating strain induced intrinsic tunnel barriers.

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Large photoresistance and photoinduced magnetoresistance in La_0.67Ca_0.33MnO₃ thin film on silicon substrate

Mohan,

Manral,

Rani

et al. 2024

J. Phys. D: Appl. Phys.

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The effects of light illumination and magnetic field on the electrical transport properties of La0.67Ca0.33MnO3 thin film on a silicon substrate have been studied in detail. Large value of colossal magnetoresistance has been observed under an applied magnetic field in the whole temperature range below 150 K which is related to the presence of both antiferromagnetic and ferromagnetic phase in the sample. A significant amount of resistance drop is caused by lightillumination even at extremely low light intensities, ~ -22% with light of 0.3 μW/cm2 intensityand ~ -42 % with 6.2 μW/cm2 intensity at 600 nm wavelength. There has been a notable rise in the photoinduced magnetoresistance value, specifically, a significant decrease in resistance occurs in simultaneous presence of magnetic field and light. For 1 T applied magnetic field, -MR% rises from -33 % in dark to -58 % under light illumination at 150 K i.e. ∆MR % is 25 %. As the strength of the magnetic field increases, ∆MR % decreases, suggesting that the magnetoresistive photoinduced phenomenon is more pronounced in the presence of mix phases in the sample. This combined enhanced magnetoresistive photoinduced phenomenon is explained by the interaction of photogenerated charge carriers in the sample and applied magnetic field.

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Anisotropic behaviour in the magnetic field dependence of the low temperature electrical resistance of calcium-doped lanthanum manganate thin films grown by RF magnetron sputtering

Cited by 3 publications

References 43 publications

Out-of-plane low field anisotropic magnetoresistance in Nd0.51Sr0.49MnO3 thin films

Out-of-plane low field anisotropic magnetoresistance in Nd0.51Sr0.49MnO3 thin films

Giant positive magnetoresistance in ultrathin films of mixed phase manganites

Large photoresistance and photoinduced magnetoresistance in La_0.67Ca_0.33MnO₃ thin film on silicon substrate

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Anisotropic behaviour in the magnetic field dependence of the low temperature electrical resistance of calcium-doped lanthanum manganate thin films grown by RF magnetron sputtering

Cited by 3 publications

References 43 publications

Out-of-plane low field anisotropic magnetoresistance in Nd0.51Sr0.49MnO3 thin films

Out-of-plane low field anisotropic magnetoresistance in Nd0.51Sr0.49MnO3 thin films

Giant positive magnetoresistance in ultrathin films of mixed phase manganites

Large photoresistance and photoinduced magnetoresistance in La0.67Ca0.33MnO3 thin film on silicon substrate

Contact Info

Product

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Large photoresistance and photoinduced magnetoresistance in La_0.67Ca_0.33MnO₃ thin film on silicon substrate