The size of magnetic media to record a single bit have decreased drastically in recently years in order to increase the capacity of storage. However, the continued decrease of grain size brings about a severe superparamagnetic limit. One of the ways to overcome the thermal stability due to superparamagnetism is to adopt higher K{sub}u materials as recording medium. However, because the magnetic field of recording heads is limited to ～15kOe, it is difficult to write the high materials. To overcome this problem the concept of the heat assisted magnetic recording (HAMR) was introduced. The basic idea of the HAMR approach is to write bits of information at an elevated temperature close to the Curie temperature, where the switching field is small, and store the information at room or slightly elevated temperature, where the thermostability ratio is high. To achieve significant areal density advantage, the use of high anisotropy intermetallics such as L1{sub}0 ordered phase FePt has been suggested[1]. When the particles are heated by laser, the temperature in the particles is usually not uniform, and has a certain distribution, for example, a Gaussian distribution. In order to shed light on the effect of the temperature distribution in particles on the magnetization switching, extensive Monte Carlo simulations have been performed. We have considered that a rectangular FePt particle of size with and assumed that the temperature in the particle has a Gaussian distribution in xoy plane, T(x,y)=T{sub}m exp{-[(x-v{sub}1){sup}2/(σ{sub}1){sup}2+(y-v{sub}2){sup}2/(σ{sub}2){sup}2]/2}, where (x, y) is the point coordinate and T{sub}m is the maximum temperature in particle and v,σ are constant, which determine the property of the distribution curve. The temperature dependent parameter saturation magnetization M and anisotropy constant K can evaluated in terms of the single-ion model of FePt. As stated in Ref.2, we have m(T)=M(T)/M(0)=[2tanh(x)+tanh(x/2)]/3=5Tx/6T{sub}c (1) k(T)=K(T)/K(0)=tanh(x)tanh(x/2) (2) where T{sub}c is the Curie temperature of FePt.
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