A study of the induced anisotropy in a ferromagnetic grain from an exchange coupled antiferromagnetic grain with uniaxial anisotropy |
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| Institution: | 1. Department of Physics, San Diego State University, San Diego, CA 92182-1233, USA;2. National High Magnetic Field Laboratory, Los Alamos, NM 87545, USA;3. Los Alamos National Laboratory, MS K764, Los Alamos, NM 87545, USA;4. National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32306, USA;1. Instituto de Fı́sica “Gleb Wataghin”, Universidade Estadual de Campinas (UNICAMP), C.P. 6165, Campinas 13083-970, SP, Brazil;2. Institute of Physics, ASCR, Na Slovance 2, CZ - 182 21 Praha 8, Czech Republic;3. Institute of Technical Physics, 47 Mangeron Blvd., 6600 Iasi 3, Romania |
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| Abstract: | Approximate analytic solutions for the energy of an antiferromagnetic (AF) grain, which experiences an external exchange torque from a ferromagnetic grain have been obtained for a wide range of AF thickness. The accuracy of the analytic expression is within 2.0% of the exact solution, which do not have a closed analytical form. The model predicts that there are two critical AF grain thickness for each particular exchange energy strength. Below the first critical thickness, the induced anisotropy energy is well approximated by an uniaxial anisotropy term. Above the second critical thickness the induced anisotropy is unidirectional. In the intermediate range the induced anisotropy can not be expressed simply as uniaxial or unidirectional. The exchange bias and coercivity in NiFe/IrMn films have been studied as a function of the IrMn thickness, and the results are consistent with the proposed theory. |
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