The NaZn13-type compounds La(Fe1−xCox)11.9Si1.1 (x=0.04, 0.06, 0.08) were successfully synthesized, in which the Si content is the limit that can be reached by arc-melting technique. TC is tunable from 243 to 301 K with Co doping from x=0.04 to 0.08. Great magnetic entropy change ΔS in a wide temperature range from ∼230 to ∼320K has been observed. The adiabatic temperature change ΔTad upon changing magnetic field was also directly measured. ΔTad of sample x=0.06 reaches ∼2.4K upon a field change from 0 to 1.1 T. The temperature hysteresis upon phase transition is small, ∼1K, for all samples. The influence of Co doping on itinerant electron metamagnetic transition and magnetic entropy change is discussed.

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The electrocaloric effect in thin films of a poly(vinylidene fluoride-trifluoroethylene chlorofluoroethylene) terpolymer (62.6/29.4/8 mol. %, 11-12 lm thick) is directly measured by infrared imaging at ambient conditions. The adiabatic temperature change is estimated to be 5.2 K for an applied electric field of 90 V/lm. The temperature change is independent of the operating frequency in the range of 0.03-0.3 Hz and is stable over a testing period of 30 min. Application of this terpolymer is promising for micro-scale refrigeration. V C 2014 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4890676] Micro-scale refrigeration systems are widely used for the cooling of integrated circuits, microelectromechanical sensors, and biomedical devices.1 Environment-friendly cooling technologies with a high efficiency are attractive due to growing energy demands and stringent environmental requirements. 2Although thermoelectric cooling is commonly applied and has been scaled to the micro-domain, 3-6 the low efficiency and challenges in material fabrication suggest that alternatives are needed. 6 While refrigeration based on the magnetocaloric effect 7 can be employed to achieve extremely low temperatures, miniaturization of devices is challenging while maintaining a high cooling performance due to the difficulty of realizing the large magnetic fields required. 2The electrocaloric (EC) effect is a phenomenon in which reversible, polarization-related temperature and entropy changes occur when an electric field is applied to certain materials. EC cooling, which operates on a refrigeration cycle analogous to magnetocaloric cooling, is an emerging technology. 8 The highest reported adiabatic temperature change in a bulk EC material is 2.5 K at an electric field of 3 V/lm and a temperature of 434 K 11 The P(VDF-TrFE-CFE) terpolymer demonstrates an adiabatic temperature change of 16 K at an electric field of 150 V/lm near room temperature 12 and is easily and economically fabricated, making it favorable for mass production.13 These findings point to the potential of applying EC cooling in micro-devices using polymer thin films.Direct and indirect techniques can be applied to measure the EC effect. In the indirect measurement, a differential scanning calorimeter is used to measure the heat flow under a high electric field and isothermal conditions. 14,15 This technique is best suited to bulk materials as the output heat flow signal for a thin film sample is very small. Jia and Ju 16 reported an approach for characterizing the EC effect in a thin film sitting on an insulating substrate. In this approach, the temperature response of a resistance thermometer deposited on the bottom of the EC film is monitored as an electric field is turned on and off. In the reported measurements, the temperature change is less than 10% of that expected because the heat loss from the EC film to the substrate is large. Lu et al.17 employed a specially designed calorimeter to measure the EC effect in a thin film. In this approach, the heat generated in the...

Multiferroic behavior was directly verified in a laminated ferroelectric-ferromagnetic heterostructure consisting of a FeCoV thick film ͑70 m͒ and lead zinc niobate-lead titanate ͑PZN-PT͒ single crystal. This unique heterostructure demonstrates a significant converse magnetoelectric ͑CME͒ effect corresponding to a CME coupling constant of 31 Oe/ kV cm −1. It derives from the soft magnetic and magnetostrictive properties ͑ = 60 ppm͒ of FeCoV alloy and the superior electromechanical properties ͑d 32 = −2800 pC/ N͒ of PZN-PT crystal. The electric field controlled magnetic hysteresis is discussed in terms of a stress-induced anisotropy field model. The theoretical calculation is within 7% of the measured induced field of 240 Oe.

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