Magnetic relaxation and thermal properties of a two-dimensional array of dipolar-coupled nanoparticles
Magnetic relaxation and thermal properties of a two-dimensional array of dipolar-coupled nanoparticles
复制标题
偶极耦合纳米粒子二维阵列的磁弛豫和热性质
DOI：
10.1088/0953-8984/19/27/276203
复制
发表时间：
2007
期刊：
影响因子：
--
通讯作者：
W. Schwarzacher
中科院分区：
文献类型：
--
作者：
W. Figueiredo;W. Schwarzacher
我们通过蒙特卡罗模拟研究了具有随机单轴各向异性轴的磁性纳米颗粒三角形阵列的热性质。它们是偶极力耦合，我们确定的阻断温度的系统作为偶极耦合的各向异性强度和幅度的函数。我们计算的磁化强度，磁化率，比热和Binder累积量作为温度的函数，我们看到，在非相互作用的情况下，这些属性表现出最大值的阻断温度。我们发现，阻塞温度的增加与偶极相互作用引起的有效能垒的增加有关。我们还确定了作为温度和偶极强度的函数的剩磁和矫顽场的依赖性。在非常低的温度下，矫顽场显示作为偶极强度的函数的最小值。研究了具有相同单轴各向异性能的纳米颗粒组装体的磁弛豫随温度和偶极强度的变化。我们还考虑了几乎非热弛豫的行为，发生在作为偶极耦合强度的函数的弛豫过程的最开始。
We investigate through Monte Carlo simulations the thermal properties of a triangular array of identical magnetic nanoparticles with random uniaxial anisotropy axes in three dimensions. They are coupled by dipolar forces and we determine the blocking temperature of the system as a function of the anisotropy strength and magnitude of the dipolar coupling. We calculate the magnetization, susceptibility, specific heat and Binder cumulant as a function of temperature, and we see that, in the non-interacting case, these properties exhibit a maximum at the blocking temperature. We have found that the increase of blocking temperature is related to an increase in the effective energy barrier due to the dipolar interactions. We have also determined the dependence of the remanence and coercive field as a function of temperature and dipolar strength. At very low temperatures, the coercive field displays a minimum as a function of dipolar strength. The magnetic relaxation is studied as a function of temperature and dipolar strength for an assembly of nanoparticles possessing the same uniaxial anisotropy energy. We have also considered the behaviour of the almost non-thermal relaxation that occurs at the very beginning of the relaxation process as a function of the dipolar coupling strength.