Magnetic nanowires (NW) are promising candidates for heat generation under AC-field application due to their large shape anisotropy. They may be used for catalysis, hyperthermia or water purification treatments. In the present work we theoretically evaluate the heat dissipated by a single magnetic nanowire, originated from the domain wall dynamics under the action of an AC-field. We compare the Permalloy NWs (which demagnetize via the transverse wall propagation) with the Co fcc NWs whose reversal mode is via a vortex domain wall. The average hysteresis loop areas -which are proportional to the Specific Absorption Rate (SAR)- as a function of the field frequency have a pronounced maximum in the range 200MHz-1GHz. This maximum frequency is smaller in Permalloy than in Co and depends on the nanowire length. A simple model related to the nucleation and propagation time and domain wall velocity (higher for the vortex than for the transverse domain wall) is proposed to explain the non-monotonic SAR dependence on the frequency.
Spin wave mediated unidirectional Vortex Core Reversal by Two Orthogonal Monopolar Field Pulses: The Essential Role of Three-dimensional Magnetization Dynamics
利用扫描透射X射线显微镜（SEM）研究了两个正交单极磁场脉冲（峰值为$B_0$，脉冲长度为60 ps，脉冲延迟时间为-400 ~+400 ps）触发圆柱形Ni 81 Fe 19纳米盘中磁涡旋核极性反转的现象.这两个脉冲在x和y方向上定向在平面内。我们实验研究了作为$B_0$和$Δ$ t函数的涡核反转。由此产生的相图示出了大区域的单向涡核切换的切换阈值调制由于方位角自旋波的共振放大。开关行为根据第一脉冲是在x方向还是y方向上施加而显著变化。这种不对称性可以通过三维微磁模拟而不是二维模拟来再现。这种行为表明，与以前的涡核反转实验相比，三维动力学在这里是必不可少的。
Magnetization reversal mechanism of double-helix nanowires probed by dark-field magneto-optical Kerr effect
TU Wien（维也纳工业大学）；University of Loughborough（拉夫堡大学）；Instituto de Nanociencia y Materiales de Aragón, CSIC-Universidad de Zaragoza（阿拉贡纳米科学与材料研究所，西班牙科学理事会-萨拉戈萨大学）；Synchrotron SOLEIL（SOLEIL同步辐射中心）；University of Vienna（维也纳大学）；Max Planck Institute for Chemical Physics of Solids（马克斯·普朗克固体化学物理研究所）；Hiroshima University（广岛大学）
