Design and characterization of photo-controllable magnetic materials

我们报道了几个包含光致变色化合物和磁性材料的新型光开关磁系统的例子。也就是说，磁性能可以通过光致变色化合物的光异构化来控制。为了实现室温下磁化的可逆光开关，我们重点研究了纳米级磁性颗粒的表面改性，并将含偶氮苯的光致变色两亲化合物与磁性纳米颗粒结合作为室温下工作的磁性材料。磁性氧化铁纳米颗粒被含偶氮苯的两亲性化合物包裹，估计平均尺寸为5nm。偶氮部分（反式/顺式）的光异构化影响了磁性纳米颗粒周围的静电场。因此，我们能够在室温下的固态下通过光照明可逆地控制这种复合材料的磁性。然而，到目前为止报道的例子在室温下没有表现出铁磁行为。从它们在磁记录系统中的实际应用来看，能够固定它们的磁矩，使它们仍然表现出室温铁磁性是绝对需要的。在这里，我们设计了可逆的光切换铁磁FePt纳米颗粒，其表面涂有偶氮苯衍生配体。这些复合纳米颗粒即使在室温下也表现出铁磁性。在核心颗粒表面，利用间隔配体在偶氮配体之间提供足够的自由体积，实现了固态偶氮苯的可逆光异构化。这些光异构化引起了核心fept纳米粒子周围静电场的变化。因此，我们已经成功地控制了这些铁磁性复合纳米颗粒在室温下的固态交变光照明的磁性。少

We have reported several examples of novel photo-switching magnetic systems containing photochromic compounds and magnetic materials. That is, the magnetic properties can be controlled by photoisomerization of the photochromic compounds.In order to realize reversible photo switching of magnetization at room temperature, we have focused on a surface modification of nano-scale magnetic particles and a combination of photochromic azobenzene-containing amphiphilic compounds and the magnetic nanoparticles as magnetic materials that can function at room temperature. The magnetic iron oxide nanoparticles, with an estimated average size of 5nm, were encapsulated with an azobenzene-containing amphiphilic compound. Photoisomerization of the azo moiety (trans/cis) affected the electrostatic field around the magnetic nanoparticles. As a result, we were able to reversibly control the magnetic properties of this composite material by photo-illumination in the solid state at room temperature. However … More , the examples reported so far did not show ferromagnetic behavior at room temperature.From the viewpoint of their practical application to the magnetic recording systems, the ability to fix their magnetic moments such that they still exhibit room temperature ferromagnetism is an absolute requirement. Here we have designed reversible photo-switchable ferromagnetic FePt nanoparticles whose surfaces were coated with azobenzene derivatized ligands. These composite nanoparticles showed ferromagnetic behavior even at room temperature. On the surfaces of core particles, reversible photoisomerization of azobenzene in the solid state was realized by using spacer ligands which provide sufficient free volume between azo-ligands. These photoisomerization brought changes in the electrostatic field around the core-FePt nanoparticles. As a result, we have succeeded in controlling the magnetic properties of these ferromagnetic composite nanoparticles by alternating photoillumination in the solid state at room temperature. Less