权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Exploration of Novel Transition Metal Oxyarsenides

新型过渡金属砷化物的探索

基本信息

批准号：
EP/L002493/1
负责人：
Abbie Mclaughlin
金额：
$ 38.59万
依托单位：
University of Aberdeen
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2013
资助国家：
英国
起止时间：
2013 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FL002493%2F1
关键词：
Exploration Novel Transition Metal Oxyarsenides

项目摘要

Spintronic materials can exhibit a large reduction in electronic resistivity upon application of a magnetic field, called magnetoresistance. Such materials are currently employed in magnetic sensors and magnetic memory devices such as computer hard disks. The discovery of giant magnetoresistance (GMR) in multilayers consisting of magnetic and nonmagnetic thin films was a major breakthrough, allowing the storage capacity of a hard disk to increase from 1 to 20 gigabits. GMR devices can exhibit a reduction in electronic resistivity of up to 50% upon application of a magnetic field. In recent years there has been intense study into the magnetic and electronic properties of manganite perovskites such as La1-xAxMnO3 (A = Ca, Sr, Ba) due to the observation of colossal magnetoresistance (CMR). The manganites are remarkable as they can exhibit a reduction in electronic resistivity of up to 99.9 % upon application of a magnetic field. As yet the large magnetic fields required to produce the CMR has limited its commercial implementation. An important research objective therefore is to discover new materials that exhibit CMR in low fields (<<1 T) at 290 K to be employed in spintronic devices for smaller, faster, cheaper and more efficient computing applications. It is therefore vital to synthesise and investigate novel CMR materials in order to gain greater understanding of different CMR mechanisms which can then be exploited in future CMR devices. We have recently synthesised a new CMR material NdMnAsO1-xFx (x = 0.05 - 0.08) which surprisingly exhibits a reduction in electronic resistivity by 95% upon applying a magnetic field at low temperature, which is comparable to that observed in the CMR manganites. This is a new mechanism of CMR. The undoped compounds LnMnAsO (Ln = Nd, La) already exhibit a sizeable room temperature negative magnetoresistance (-MR; MR = -8% and -11% for Ln = Nd and La respectively in a 7 T magnetic field). We propose to improve the magnetoresistant properties of these fascinating Mn2+ oxyarsenides by exploring the effects of chemical substituents.We will also synthesise and study the magnetotransport properties of novel Mn2+ oxyarsenides such as Sr2Mn2MAs2O2-xFx (M = Mn, Ni, Fe, Cu) in order to manipulate the CMR by enhancing magnetic coupling between Mn2+ and M2+ cations. The magnetic and electronic properties of 3d transition metal oxyarsenides reported so far are exceptional. Alongside the observation of high temperature superconductivity in LnFeAsO1-xFx and CMR in NdMnAsO1-xFx, superconductivity has also been reported in LaNiAsO below 2.75 K whereas LnCoAsO is a ferromagnet below 66 K and 85 K for Ln = La and Nd respectively. We will investigate if novel superconducting and MR pathways are also present in 4d/5d transition metal oxyarsenide which have been relatively unexplored until now.This work will not only be of great fundamental importance but may also have practical applications if it is possible to optimise the magnetoresistive properties.

自旋电子材料在施加磁场时可以表现出电子电阻率的大幅降低，称为磁阻。这种材料目前用于磁传感器和磁存储器设备，如计算机硬盘。在由磁性和磁性薄膜组成的多层膜中发现巨磁电阻（GMR）是一项重大突破，使硬盘的存储容量从1千兆比特增加到20千兆比特。在施加磁场时，GMR器件可以表现出高达50%的电子电阻率降低。近年来，由于巨磁电阻效应（CMR）的观测，人们对钙钛矿锰氧化物如La_（1-x）AxMnO_3（A = Ca，Sr，Ba）的磁学和电学性质进行了深入的研究。锰氧化物是显著的，因为它们在施加磁场时可以表现出高达99.9%的电子电阻率降低。到目前为止，产生CMR所需的大磁场限制了其商业应用。因此，一个重要的研究目标是发现在290 K下在低场（<<1 T）中表现出CMR的新材料，以用于更小、更快、更便宜和更有效的计算应用的自旋电子器件。因此，合成和研究新型CMR材料以更好地理解不同的CMR机制是至关重要的，然后可以在未来的CMR器件中利用这些机制。我们最近合成了一种新的CMR材料NdMnAsO 1-xFx（x = 0.05 - 0.08），其在低温下施加磁场时令人惊讶地表现出电子电阻率降低95%，这与在CMR锰氧化物中观察到的相当。这是CMR的一种新机制。未掺杂的化合物LnMnAsO（Ln = Nd，La）已经表现出相当大的室温负磁电阻（-MR;在7 T磁场中，Ln = Nd和La的MR分别为-8%和-11%）。我们还将合成并研究新型Mn ~（2+）砷氧化物Sr_2Mn_2MAs_2O_2-xFx（M = Mn，Ni，Fe，Cu）的磁输运性质，以期通过增强Mn ~（2+）和M ~（2+）阳离子之间的磁耦合来调控CMR。迄今报道的3d过渡金属砷氧化物的磁学和电学性质都是非常出色的。除了在LnFeAsO 1-xFx中观察到高温超导性和在NdMnAsO 1-xFx中观察到CMR外，LaNiAsO在2.75 K以下也有超导性，而LnCoAsO在66 K和85 K以下分别为Ln = La和Nd时是铁磁体。我们将研究新的超导和MR路径也存在于4d/5d过渡金属砷氧化物已相对未开发到现在为止，这项工作不仅将是非常重要的，但也可能有实际应用，如果它是可能的，以优化磁阻性能。