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Etude par simulations numériques de bicouches FM/AFM à anisotropie d'échange

Abstract : This thesis is dedicated to the study, by mean of Monte Carlo simulations, of the exchange anisotropy observed in MRAMs. The first part of the manuscript focuses on the influence of the interfacial roughness and the temperature, on exchange anisotropy properties, via an atomic approach. This study confirmed the strong influence of the interfacial configuration. It was observed that a roughest interface gives rise to higher values of the exchange field. Moreover, the presence of FM sites with a strong local field, acting as nucleation sites during the magnetization reversal, has been observed. Our results have shown that magnetic frustration, combined to thermal activation, with a sufficiently rough interface, can lead to a cancelling of the exchange field, confirming that magnetic frustration at FM/AFM interface can lead, when the temperature increases, to magnetically disordered areas which do not contribute to the exchange field. The second part of the manuscript is dedicated to the effect of temperature and microstructure on exchange anisotropy properties as well as blocking temperature distribution via a granular approach. It appears that the temperature corresponding to the disappearing of exchange field, commonly defined as the blocking temperature of AFM grains (T AF M B ), corresponds, according to our simulation, to 80% of calculated T AF M B . The influence of spin glasses areas, inducing an effective coupling decrease due to the roughness, on the T AF M B distribution has been studied. The introduction of a quantity of grains with a spin glass behavior in the AFM layer, can lead to the observation of a low temperature peak in the blocking temperature distribution, as experimentally observed.
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Submitted on : Monday, December 3, 2012 - 12:07:52 PM
Last modification on : Tuesday, October 19, 2021 - 4:14:14 PM
Long-term archiving on: : Monday, March 4, 2013 - 3:46:57 AM


  • HAL Id : tel-00760007, version 1


Adeline Maitre. Etude par simulations numériques de bicouches FM/AFM à anisotropie d'échange. Science des matériaux [cond-mat.mtrl-sci]. Université de Rouen, 2012. Français. ⟨NNT : ⟩. ⟨tel-00760007⟩



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