Maximal tunnel magnetoresistance in magnetic nanoparticle arrays with perpendicular anisotropy

We study tunnel magnetoresistance (TMR) ratio of self-assembled 2d magnetic nanoparticle (MNP) arrays by modeling them as interacting dipoles on a triangular lattice, which is representative of experimentally obtained assemblies. Low-temperature Monte Carlo simulations are performed to understand the effects of dipolar interactions and uniaxial anisotropy on TMR behavior. In magnetic tunnel junctions with a perfect antiparallel state, the TMR amplitude reaches the ideal value 2P2/(1−P2), where P is the spin polarization. We show that, for MNPs with their anisotropy axes perpendicular to the array, the TMR amplitude can reach a value as large as 2400%, which represents an order of magnitude improvement over previous studies. We evaluate the conditions for which these large amplitudes could be obtained experimentally at room temperature and find that spherical MNPs with large magnetocrystalline anisotropy or nanorods are suitable candidates. Our theoretical results should stimulate experimental groups into elaborating the samples proposed in this work, which could display large TMR amplitudes.