Response of magnetic nanoparticles to microwaves
Response of magnetic nanoparticles to microwaves
复制标题
磁性纳米粒子对微波的响应
DOI：
10.1063/1.1829771
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发表时间：
2004
影响因子：
4
通讯作者：
D. Dunlop
中科院分区：
文献类型：
--
作者：
D. Walton;H. Boehnel;D. Dunlop
铁磁共振中的两个重要过程是光子的一阶吸收和单个磁振子的产生，以及光子的吸收导致产生两个波矢相等且相反的磁振子的二阶过程[M. Sparks，Ferromagnetic Relaxation（McGraw-Hill，纽约，1964）]。我们发现，在二阶过程的共振条件下，含有0.01%磁铁矿的样品从微波场吸收能量的速率与固体磁铁矿样品相同。在磁性纳米颗粒中产生的非常高的能量密度，加上与基质的显著的热能屏障，导致晶粒与其周围环境之间的大温差，这使得可以在样品温度相对较小的增加下磁化和退磁样品。
Two important processes in ferromagnetic resonance are the first-order absorption of a photon and creation of a single magnon, and a second-order process in which the absorption of a photon results in the creation of two magnons of equal and opposite wave vector [M. Sparks, Ferromagnetic Relaxation (McGraw–Hill, New York, 1964)]. We have found that under resonance conditions for the second-order process, samples containing ∼0.1% magnetite absorb energy from the microwave field at the same rate as a solid magnetite sample. The resultant very high-energy density in the magnetic nanoparticles, coupled with a significant thermal energy barrier with the matrix, leads to a large temperature difference between the grains and their surroundings that makes it possible to magnetize and demagnetize the sample with a relatively small increase in sample temperature.