Tuning the Metal-Insulator Transition in Manganite Films through Surface Exchange Coupling with Magnetic Nanodots

Abstract

In strongly correlated electronic systems, such as manganites, the global transport behavior depends sensitively on the spin ordering, whose alteration often requires a large external magnetic field. Here we show that the spin ordering in manganites can be easily controlled by exchange field across the interface between a ferromagnet and a manganite. By depositing isolated ferromagnetic nanodots on a manganite thin film, we find that it is possible to overcome dimensionality and strain effects to raise the metal-insulator transition (MIT) temperature by over 200 K and increase the magnetoresistance by 5000%. The MIT temperature can also be tuned by controlling the density of the magnetic nanodots which indicates that the formation process of electronic phase separation can be controlled by the presence of magnetic nanodots.Complex electronic systems exhibit a wide range of fascinating and potentially useful behaviors such as, colossal magnetoresistance (CMR), multiferroicity and high T c superconductivity. Thin films of these materials are particularly interesting for two reasons: 1) The physical parameters such as strain and dimensionality can be easily accessed to control the physical properties of the system; 2) Many practical applications require the materials to be prepared in thin film form. However, in many cases, the reduced dimensionality and strain effects can act against long range ordering and lead to critical temperatures that are too low for practical applications or lead to a loss of exotic properties altogether [1][2][3][4][5][6][7][8]. Restoring the long range order often requires impractically high external fields.

Visualization of a ferromagnetic metallic edge state in manganite strips

“…However, since the electronic states in the phase-separated conditions are very sensitive to the environment, these nanoscale edge states could have as a seed and trigger even larger scale edge phases in the real mesoscopic strip. This kind of seeding effect on LPCMO surface has been observed through surface exchange coupling with ferromagnetic iron nanodots 24 . Moreover, the width of edge phases at initial stage acquired by MFM is B1 mm, which is the typical length scale of EPS domains in LPCMO.…”

Intrinsic and precipitate-induced quantum corrections to conductivity in La2/3Sr1/3MnOGao1, Cao2, Zhang3 et al. 2012Phys. Rev. B

“…[1][2][3][4][5][6] In the past decade, several papers have been published claiming the presence of quantum interference effects in the low temperature region of the magnetotransport properties which give rise to resistivity minim, ρ min , below ~ 40K. [7][8][9][10] These resistivity minima-appearing to be similar to those of Kondo systems -were observed in manganite bulk ceramics, 11 polycrystalline as well as high quality epitaxially grown films and in single crystals. [12][13][14][15] Extensive experimental and theoretical work has been performed, and several mechanisms have been discussed to interpret these resistivity minima.…”

Strain driven anisotropic magnetoresistance in antiferromagnetic La0.4Sr0.6MnO3

“…4,5 While strongly correlated oxides are considered to have immense promise in next generation electronic and sensing devices, few studies exist for AFM spintronic applications. [5][6][7][8][9][10] In most cases, these materials have rich electron/hole doping phase diagrams populated with vastly different resistive and magnetic properties. Dopings that lie near phase boundaries are often of particular interest due to their high sensitivity to perturbations in their underlying spin-charge-orbital order parameters, which can lead to colossal changes in resistive and magnetic properties.…”