Thermal relaxation rates of magnetic nanoparticles in the presence of magnetic fields and spin-transfer effects
Thermal relaxation rates of magnetic nanoparticles in the presence of magnetic fields and spin-transfer effects
复制标题
磁场和自旋转移效应存在下磁性纳米粒子的热弛豫率
DOI：
10.1103/physrevb.84.064439
复制
发表时间：
2011
影响因子：
3.7
通讯作者：
A. Kos
中科院分区：
文献类型：
--
作者：
W. Rippard;R. Heindl;M. Pufall;S. Russek;A. Kos
我们已经测量了一个热不稳定的铁磁纳米粒子纳入磁性隧道结（MTJ）的弛豫时间作为施加磁场，电压V（-0.38 V < V < +0.26 V），和温度（283 K< T< 363 K）的函数。通过分析的结果在一个修改后的Neel-Brown形式主义的框架内，我们确定的纳米粒子的有效尝试时间，也在平面和平面外的自旋扭矩的偏置依赖性。由于面内扭矩和与电压成二次关系的“类场”扭矩的显著贡献，有效温度与电压存在显著的线性修改。这里提出的方法不需要复杂的器件加热或校准程序模型，而是直接测量温度、场和电压如何影响双态系统的能量分布和热波动。这些结果对未来纳米级磁性随机存取存储器元件的设计具有重要意义，并提供了一种简单的方法来确定其他MTJ器件结构中的这些参数。
We have measured the relaxation time of a thermally unstable ferromagnetic nanoparticle incorporated into a magnetic tunnel junction (MTJ) as a function of applied magnetic field, voltage V (-0.38 V < V < +0.26 V), and temperatures (283 K< T< 363 K) . By analyzing the results within the framework of a modified Neel-Brown formalism we determine the effective attempt time of the nanoparticle and also the bias dependences of the in-plane and out-of-plane spin torques. There is a significant linear modification of the effective temperature with voltage due to the in-plane torque and a significant contribution of a "field like" torque that is quadratic with voltage. The methods presented here do not require complicated models for device heating or calibration procedures, but instead directly measure how temperature, field, and voltage influence the energy landscape and thermal fluctuations of a two-state system. These results should have significant implications for designs of future nanometer-scale magnetic random access memory elements and provide a straightforward methodology to determine these parameters in other MTJ device structures.