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As a platinum group metal, iridium (Ir) is the scarcest element on the earth but it has been widely used as an antiferromagnetic layer in magnetic recording, crucibles and spark plugs due to its high melting point. In magnetic recording, antiferromagnetic layers have been used to pin its neighbouring ferromagnetic layer in a spin-valve read head in a hard disk drive for example. Recently, antiferromagnetic layers have also been found to induce a spin-polarised electrical current. In these devices, the most commonly used antiferromagnet is an Ir–Mn alloy because of its corrosion resistance and the reliable magnetic pinning of adjacent ferromagnetic layers. It is therefore crucial to explore new antiferromagnetic materials without critical raw materials. In this review, recent research on new antiferromagnetic Heusler alloys and their exchange interactions along the plane normal is discussed. These new antiferromagnets are characterised by very sensitive magnetic and electrical measurement techniques recently developed to determine their characteristic temperatures together with atomic structural analysis. Mn-based alloys and compounds are found to be most promising based on their robustness against atomic disordering and large pinning strength up to 1.4 kOe, which is comparable with that for Ir–Mn. The search for new antiferromagnetic films and their characterisation are useful for further miniaturisation and development of spintronic devices in a sustainable manner.

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We report on a low-cost, innovative approach for synthesizing prepatterned, magnetic nanostructures, the shapes and dimensions of which can be easily tuned to meet requirements for next-generation data storage technology. The magnetic nanostructures consist of self-assembled Co nanodots and nanowires embedded in yttria-stabilized zirconia (YSZ) matrices. The controllable size and aspect ratio of the nanostructures allows the selection of morphologies ranging from nanodots to nanowires. Co nanowires show strong shape anisotropy and large remanence at 300 K. In contrast, Co nanodots display minimal effects of magnetocrystalline anisotropy and superparamagnetic relaxation above the blocking temperature. These prepatterned magnetic nanostructures are very promising candidates for data storage technology with an ultrahigh density of 1 terabit in(-2) or higher.

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