The effect of the total density of states at Fermi level on spin polarised tunnelling in granular La0.55Ho0.15Sr0.3MnO3

We study the spin polarised tunnelling mechanism through magnetisation and magnetoresistance in the granular polycrystalline colossal magnetoresistive manganite, La0.55Ho0.15Sr0.3MnO3. This system has a ferromagnetic transition temperature (Tc) of 255 K associated with a metal-insulator transition around the same temperature. We have investigated dependence of the magnetoresistance due to spin polarised tunnelling on temperature and reduced magnetisation of the sample. We discuss the significance of our results within the realm of a model recently proposed by us to explain the spin polarised tunnelling in granular La0.7Sr0.3MnO3, in the light of the recent finding by A. Biswas et al. (cond-mat/9806084) regarding the evolution of the total density of states at Fermi level as a function of temperature in colossal magnetoresistive materials.