Design and magnetic properties of L10–FePt/Fe and L10–FePt exchange coupled graded nanodots

• The magnetic properties and reversal process of L10–FePt/Fe and L10–FePt exchange coupled graded nanodots were investigated using the object-oriented micromagnetic framework.
• The increase in anisotropy gradient span of L10–FePt section is favorable for the reduction in coercivity for L10–FePt/Fe graded nanodots.
• The low coercivity and high squareness ratio can be achieved simultaneously for L10–FePt graded nanodots with an appropriate gradient design.

The magnetic properties and reversal process of L10–FePt/Fe and L10–FePt exchange coupled graded nanodots were investigated using the object-oriented micromagnetic framework (OOMMF). It is indicated that the increase in anisotropy gradient span of L10–FePt section is favorable for the reduction in coercivity for L10–FePt/Fe graded nanodots. However, the low remanence magnetization and squareness ratio caused by the large gradient span is not popular for recording media. If the Fe soft section is removed, the low coercivity and high squareness ratio can be achieved simultaneously for L10–FePt graded nanodots with an appropriate gradient design. Therefore, the combination of exchange coupled graded structure and bit patterned media is an effective approach to balance the trilemma issues of current perpendicular magnetic recording media.

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