标准化——认证的道路

早在20世纪70年代,人们使用电脑,主要将它视为一种集尖端科技于一身的工具。20世纪80年代初期,个人电脑也走入了部分办公机构,也成为一种必不可少的办公工具。但在那时,由于高昂的售价,个人电脑并没有被大范围普及。部分电脑产品虽然加入了些许安全措施,可在那个时代,这也许并不重要。直到20世纪80年代末,个人电脑才放下了高贵的姿态走入了更多人的生活当中。可随之而来的危害和事故却是却是电脑带来的,眩晕、耳鸣、呕吐、视力下降等症状正是长时间使用电脑导致的;触电、起火、爆炸也是等事故的始作俑者竟然也是电脑。人们不禁要问,电脑虽然是高科技的产物,但和脆弱的人体搭配是否有失安全。因此,各国科学家为了解决这些难题,遂投身于一个新的工作——电器标准认证。从此,电脑产品的认证序幕便拉开了。 如今,我们在购买电脑产品时,总是关心着产品的规格、性能以及价格。但我们是否在这时考虑过这些产品经过了哪些认证?虽然这些认证不被人所熟知,但这些配件在我们日常使用中与我们又有着异常紧密的联系。 我们这次给大家介绍的不仅是这些认证的内容,更多的是给大家讲解在购买电脑配件时应注意的认证相关要素。     

Giant Electric Field Tuning of Magnetic Properties in Multiferroic Ferrite/Ferroelectric Heterostructures

Multiferroic heterostructures of Fe₃O₄/PZT (lead zirconium titanate), Fe₃O₄/PMN‐PT (lead magnesium niobate‐lead titanate) and Fe₃O₄/PZN‐PT (lead zinc niobate‐lead titanate) are prepared by spin‐spray depositing Fe₃O₄ ferrite film on ferroelectric PZT, PMN‐PT and PZN‐PT substrates at a low temperature of 90 °C. Strong magnetoelectric coupling (ME) and giant microwave tunability are demonstrated by a electrostatic field induced magnetic anisotropic field change in these heterostructures. A high electrostatically tunable ferromagnetic resonance (FMR) field shift up to 600 Oe, corresponding to a large microwave ME coefficient of 67 Oe cm kV^?1, is observed in Fe₃O₄/PMN‐PT heterostructures. A record‐high electrostatically tunable FMR field range of 860 Oe with a linewidth of 330–380 Oe is demonstrated in Fe₃O₄/PZN‐PT heterostructure, corresponding to a ME coefficient of 108 Oe cm kV^?1. Static ME interaction is also investigated and a maximum electric field induced squareness ratio change of 40% is observed in Fe₃O₄/PZN‐PT. In addition, a new concept that the external magnetic orientation and the electric field cooperate to determine microwave magnetic tunability is brought forth to significantly enhance the microwave tunable range up to 1000 Oe. These low temperature synthesized multiferroic heterostructures exhibiting giant electrostatically induced tunable magnetic resonance field at microwave frequencies provide great opportunities for electrostatically tunable microwave multiferroic devices.