On beating the superparamagnetic limit with exchange bias
On beating the superparamagnetic limit with exchange bias
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DOI：
10.1209/0295-5075/88/57004
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发表时间：
2009-12
期刊：
影响因子：
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通讯作者：
R. Evans;R. Yanes;O. Mryasov;R. Chantrell;O. Chubykalo-Fesenko
中科院分区：
文献类型：
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作者：
R. Evans;R. Yanes;O. Mryasov;R. Chantrell;O. Chubykalo-Fesenko
为了研究“用交换偏置击败超顺磁极限”的可能性（Skumryev V. Nature，423（2003）850），我们对改变铁磁体/反铁磁体界面耦合强度的Co/CoO磁性纳米颗粒进行原子建模。我们的结果表明，交换偏置系统表现出增加的能量势垒沿着偏置方向，与相应的减少的障碍，在相反的方向。对于具有大的界面耦合值的系统，铁磁芯被发现是无条件稳定的偏置方向。如果反铁磁壳层不变，这样的系统对于热稳定性来说是理想的，因为不存在能量稳定的反向状态。为了允许磁记录，这基本上需要一个双稳态系统，我们提出了一种热辅助记录方法，其中铁磁体（FM）和反铁磁体（AF）的切换。加热至CoO的Néel温度后，AF磁序被破坏，允许用小的外加场切换FM磁芯，通过TN冷却时重新出现热稳定性。
In order to investigate the possibility of “beating the superparamagnetic limit with exchange bias” (Skumryev V. et al., Nature, 423 (2003) 850) we perform atomistic modeling on Co/CoO magnetic nanoparticles varying the strength of the ferromagnet/antiferromagnet interfacial coupling. Our results show that exchange-biased systems exhibit an increased energy barrier along the bias direction, with a corresponding decrease of the barrier in the opposite direction. For systems with large values of the interfacial coupling, the ferromagnetic core is found to be unconditionally stable in the bias direction. Such a system is ideal for thermal stability since there is no energetically stable reversed state, providing the antiferromagnetic shell is unchanged. In order to permit magnetic recording, which essentially requires a bi-stable system, we propose a heat-assisted recording method, whereby both the ferromagnet (FM) and antiferromagnet (AF) are switched. Upon heating to the Néel temperature of CoO, the AF magnetic order is destroyed allowing switching of the FM core with a small applied field, with thermal stability reappearing on cooling through TN.