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Using ferromagnetic La0.67Sr0.33MnO3 electrodes bridged by single-layer graphene, we observe magnetoresistive changes of ~32-35 MΩ at 5 K. Magneto-optical Kerr effect microscopy at the same temperature reveals that the magnetoresistance arises from in-plane reorientations of electrode magnetization, evidencing tunnelling anisotropic magnetoresistance at the La0.67Sr0.33MnO3-graphene interfaces. Large resistance switching without spin transport through the non-magnetic channel could be attractive for graphene-based magnetic-sensing applications. [ABSTRACT FROM AUTHOR]

We show that scanning thermal microscopy can measure reversible electrocaloric (EC) effects in <40 μm-thick ceramic films of the relaxor ferroelectric 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3, with the substrate present. We recorded roughly the same non-adiabatic temperature change (±0.23 K) for a thinner film that was driven harder than a thicker film (±31 V μm−1 across 13 μm versus ±11 V μm−1 across 38 μm), because the thicker film lay relatively closer to the substantially larger adiabatic values that we predicted by thermodynamic analysis of electrical data. Film preparation was compatible with the fabrication of EC multilayer capacitors, and therefore our measurement method may be exploited for rapid characterisation of candidate films for cooling applications. [ABSTRACT FROM AUTHOR]

Energy harvesting from ambient vibrations originating from sources such as moving parts of machines, fluid flow and even body movement, has enormous potential for small power applications, such as wireless sensors, flexible, portable and wearable electronics, and bio-medical implants, to name a few. Nanoscale piezoelectric energy harvesters, also known as nanogenerators (NGs), can directly convert small scale ambient vibrations into electrical energy. Scavenging power from ubiquitous vibrations in this way offers an attractive route to provide power to small devices, which would otherwise require direct or indirect connection to electrical power infrastructure. Ceramics such as lead zirconium titanate and semiconductors such as zinc oxide are the most widely used piezoelectric energy harvesting materials. This review focuses on a different class of piezoelectric materials, namely, ferroelectric polymers, such as polyvinlyidene fluoride (PVDF) and its copolymers. These are potentially superior energy harvesting materials as they are flexible, robust, lightweight, easy and cheap to fabricate, as well as being lead free and biocompatible. We review some of the theoretical and experimental aspects of piezoelectric energy recovery using Polymer-based NGs with a novel emphasis on coupling to mechanical resonance, which is relevant for efficient energy harvesting from typically low frequency (,1 kHz) ambient vibrations. The realisation of highly efficient and low cost piezoelectric polymer NGs with reliable energy harvesting performance could lead to wide ranging energy solutions for the next generation of autonomous electronic and wireless devices. [ABSTRACT FROM AUTHOR]

A magnetically, electrically or mechanically responsive material can undergo significant thermal changes near a ferroic phase transition when its order parameter is modified by the conjugate applied field. The resulting magnetocaloric, electrocaloric and mechanocaloric (elastocaloric or barocaloric) effects are compared here in terms of history, experimental method, performance and prospective cooling applications. [ABSTRACT FROM AUTHOR]

We used finite element analysis to model the flow of heat in multilayer capacitors (MLCs) that comprise good electrocaloric materials and high-thermal-conductivity electrodes. An ideal heat pump based on these MLCs could develop a sustained cooling power of 81.7kW m-2. This supersedes the 36 kW m-2 predicted by a lumped thermal model [S. Kar-Narayan and N. D. Mathur, Appl. Phys. Lett. 95, 242903 (2009)]. We show that geometrical optimization increases predicted cooling power to 215 kW m-2. [ABSTRACT FROM AUTHOR]

We argue that the multilayer capacitor (MLC) geometry is ideal for electrocaloric cooling. Thermal modeling predicts that a commercially available MLC, which serendipitously shows electrocaloric effects, could constitute the heart of an idealized heat pump delivering a continuous cooling power of 22.5 W kg-1. This figure could be increased via materials optimization to ∼2875 W kg-1, such that an MLC array whose sheet area is just ∼0.56 m2 would deliver the ∼20 kW cooling power of typical air-cooled chillers for air-conditioning at residential and commercial sites. Expensive materials are not required, and performance could be further enhanced via geometrical improvements. [ABSTRACT FROM AUTHOR]

We report electrically induced changes of 20% in both the remnant magnetization and the coercive field of a magnetoelectric heterostructure. This heterostructure is an industrially produced multilayer capacitor comprising Ni-based magnetostrictive electrodes sandwiching a BaTiO3-based dielectric that is ferroelectric and therefore piezoelectric. Both magnetization and strain are shown to be hysteretic with applied electric field. These inexpensive capacitors might find use as electrically controlled ferromagnets. [ABSTRACT FROM AUTHOR]

We present two techniques for directly measuring electrocaloric temperature change in a multilayer capacitor based on BaTiO3. Scanning thermal microscopy with resolution 80 mK, and infra-red imaging with resolution 25 mK, each record electrocaloric temperature changes of ∼0.5 K that match within error. We find that scanning thermal microscopy is more suitable for detecting giant electrocaloric effects in thin films with substrates present. [ABSTRACT FROM AUTHOR]