www.advmat.de www.MaterialsViews.com

COMMUNICATION

Electric Field Control of the Magnetocaloric Effect Yuan-Yuan Gong, Dun-Hui Wang,* Qing-Qi Cao, En-Ke Liu, Jian Liu, and You-Wei Du Magnetoelectric (ME) coupling has attracted ever-increasing interest due to its novel physical mechanism and potential applications.[1–6] One promising approach to attain the coupling between magnetic and electric orders concerns the use of magnet/piezoelectric bilayer structures, in which excellent ME performance can be realized using strain-mediated mechanism.[7–10] Up to now, large ME effects have been experimentally observed in various systems, demonstrating the electric field manipulation of magnetic anisotropy, saturation magnetization, exchange bias, magnetization reversal, domain wall motion, and Curie temperature,[11–20] which are meaningful for the design of low-power ME devices. However, electric field control of those magnetic behaviors are far from enough to fully utilize the ME effect. Here, we show that the magnetocaloric effec (MCE), which is an important application of magnetic materials, can be significantly improved by an electric-field-controlled method. Magnetic refrigeration, which is based on MCE, is regarded as an environment friendliness and high-efficiency refrigerating technology for substituting conventional vapor compression refrigeration in the future.[21,22] Giant MCEs have been found in some magnetic oxides and alloys involving sharp magnetic transitions, such as perovskite manganites,[23] Gd5Si4-xGex,[24,25] La(Fe1-xSix)13,[26,27] MnFeP1-xAsx,[28] FeRh,[29] and so on. In the bilayer ME structure containing one of these materials and piezoelectric, the generated stress from the piezoelectric can affect the magnetic properties, leading to some interesting effects. For example, in a FeRh/BaTiO3 heterostructural structure, the transferred stress modifies the first-order transition

Dr. Y.-Y. Gong, Prof. D.-H. Wang, Dr. Q.-Q. Cao, Prof. Y.-W. Du National Laboratory of Solid State Microstructures & Jiangsu Key Laboratory for Nano Technology Department of Physics Nanjing University Nanjing 210093, P.R. China E-mail: [email protected] Dr. Y.-Y. Gong, Prof. D.-H. Wang, Prof. Y.-W. Du Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093, P.R. China Dr. E.-K. Liu State Key Laboratory for Magnetism Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190, P.R. China Prof. J. Liu Key Laboratory of Magnetic Materials and Devices Ningbo Institute of MaterialTechnology and Engineering Chinese Academy of Sciences Ningbo 315201, P.R. China

DOI: 10.1002/adma.201404725

Adv. Mater. 2014, DOI: 10.1002/adma.201404725

temperature of FeRh film, showing a large ME effect.[30] While in a La0.7Ca0.3MnO3/BaTiO3 bilayer structure, through the stress generated from the phase transformation of BaTiO3, a first-order-like transition is induced in the film, resulting in a reversible MCE.[31] It is well known that Heusler-type NiMnX (X = In, Sn, Sb) alloys can show large inverse MCE owing to the magnetic-field-induced martensitic transformation.[32–36] Since the magnetic interaction and martensitic transformation in NiMnX ferromagnetic shape memory alloys (FSMAs) are very sensitive to the stress,[37–39] their magnetic properties can be modified in a NiMnX/piezoelectric laminate through the stress transferred from the piezoelectric. Taking advantage of this effect, the manipulation of MCE by electric field is likely to be realized in NiMnX alloys. As we know, there are two important hurdles that must be overcome to fulfill Ni–Mn–X FSMAs for magnetic refrigeration. One is the limited operating temperature region and the other is the large thermal and magnetic irreversibility, both of which are due to the nature of first-order magnetic transition.[35,40,41] In this work, we demonstrate that the aforementioned problems can be effectively solved by electric field control of MCE. Moreover, we also show that, using this effect, the working efficiency of active magnetic refrigerator (AMR) can be greatly enhanced. For investigating the manipulation of MCE by electric field, the selection of magnetic cooling material is crucial, which should meet three requirements: (a) have large MCE; (b) operate around room temperature; and (c) be sensitive to external stress. In this context, the Ni–Mn–Co–In alloy seems to be an ideal candidate, as it can show giant MCE at room temperature and its magnetostructural transformation temperature (Tt) can be easily shifted by external stress.[35,37–39] As we know, the ME effect in the laminated structure is highly dependent on the thickness of the magnetic and piezoelectric layers.[16,42] For example, in the La0.7Sr0.3MnO3/Pb(Mg1/3Nb2/3) O3–PbTiO3 (PMN-PT) heterostructural film, the electric-fieldinduced change of Curie temperature is larger in a thinner La0.7Sr0.3MnO3 film.[16,42] Thus, in the present work, we prepare the Ni44Co5.2Mn36.7In14.1 (NiCoMnIn) ribbon instead of bulk alloy and combine it with PMN-PT substrate to investigate the effect of electric field on MCE. Figure 1a shows the thermomagnetic curves (M–T) for the laminate in a magnetic field of 0.01 T under the electric fields of 0, 4, and 8 kV cm−1. Under zero electric field, this sample shows a typical thermally induced martensitic transformation between a low-temperature weak magnetic martensite and a high-temperature ferromagnetic austenite. With the application of electric field, the magnetization decreases with increasing electric field and Tt shows an obvious shift to the higher temperature in the heating and cooling process, indicating an obvious ME effect. As shown in the inset of Figure 1a, the ribbon can return to its initial magnetic state with the electric field switching off, implying that this ME effect is reversible.

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

wileyonlinelibrary.com

1

www.advmat.de

COMMUNICATION

www.MaterialsViews.com

Figure 1. Thermal and magnetic field induced magnetostructural transformation under different electric fields. a) M–T curve for the NiCoMnIn ribbon in a magnetic field of 0.01 T with electric fields of 0 (squares), 4 (open triangles), and 8 kV cm−1 (solid triangles) applying on the PMN-PT substrate, respectively. Inset: With the electric field switching off, the sample can return to its initial magnetic state. b) M–H curves measured at 285 K under 0 (squares), 4 (open triangles), and 8 kV cm−1 (solid triangles), respectively.

It is known that, the exchange interaction in Ni–Mn–X alloys is very sensitive to the Mn–Mn distance.[38] In the NiCoMnIn/ PMN-PT laminate, when an electric field is applied on the PMN-PT substrate, an in-plane compression is generated due to the converse piezoelectric effect (as shown in Figure S2, Supporting Information), which would induce the crystal distortion of NiCoMnIn as well as Mn–Mn distance, leading to the variation of exchange interaction.[38] As a result, a change of magnetization and a shift of Tt are observed in NiCoMnIn ribbon. As shown in Figure 1a, the increase of Tt is about 2 K in the heating process but 7 K in the cooling process with the electric field increasing from 0 to 8 kV cm−1. This result is different from that under the constant pressure, in which the increase of Tt is almost the same in the heating and cooling process.[37–39] Such a difference is due to the fact that the compressive stress generated from PMN-PT is not constant but increases with decreasing temperature, as shown in Figure S2 (Supporting Information). Thus, a larger shift of Tt is observed in the cooling process. It is obvious that the thermal hysteresis,

2

wileyonlinelibrary.com

which is defined as the difference of Tt between the heating and cooling processes, decreases from 25.5 to 21.6 K with the electric field varying from 0 to 8 kV cm−1. As mentioned above, the reduction of thermal hysteresis under the electric field would be ascribed to the different changes of Tt in the cooling process and heating process. Figure 1b shows the isothermal magnetization (M–H) curves for NiCoMnIn/PMN-PT laminate measured at 285 K under different electric fields. With increasing magnetic field, a metamagnetic behavior is observed, corresponding to the magnetic-field-induced martensitic transformation. By applying an electric field, the magnetization decreases significantly due to the change of exchange interaction,[37,38] which in turn manifests itself in the remarkable reduction of magnetic hysteresis. Based on the M–T curves in different magnetic fields and electric fields, we calculate the adiabatic temperature change (ΔTad) for NiCoMnIn ribbon using a phenomenological model, which reliability is confirmed by the direct measurement of MCE.[35] The introduction about this model and the calculation is described in the Supporting Information. Figure 2a,b show the temperature dependence of ΔTad for NiCoMnIn in the heating and cooling process, respectively. For the heating process, the minima of ΔTad vary from −5.9 to −5.7 K with the electric field increasing from 0 to 8 kV cm−1, for which absolute values are larger than that of Gd under the same magnetic field (4.5 K at 297 K).[35] As shown in Figure 2b, an enhancement of ΔTad with the electric field is observed in the cooling process, decreasing from −5.1 K for 0 kV cm−1 to −5.4 K for 8 kV cm−1. Unlike the heating process, the peak temperature for MCE in the cooling process shows a larger shift to higher temperature by applying electric field, which is consistent with the result in Figure 1a. We also measure the M–H curves in some selected temperature under different electric fields using the so-called loop process.[43] Based on these curves, the magnetic entropy changes (ΔS) in cooling and heating process are calculated by Maxwell relation,[44] which are shown in Figure 2c,d, respectively. It is clear that ΔS shows the same electric field dependence as ΔTad, while the peak values of ΔS at 2 T are around 16 J kg−1 K−1, which are comparable to the value reported in ref. [35]. Recently, a giant solid-state barocaloric effect was observed in Ni–Mn–In FSMA by applying or withdrawing an external pressure.[45] Analogous to this work, a similar caloric effect would be realized in NiCoMnIn/PMN-PT laminate by switching on/ off the electric field. The theoretical result reveals that it is possible to enlarge the operating temperature region by simultaneously and continuously varying the magnetic field and pressure on the refrigerant.[46] Based on it, Figure 3 shows a schematic image of obtaining MCE with broad operating temperature region, in which the red and blue curves represent the MCE at fixed electric fields E1 and E2, respectively. As described in ref. [46], if we continuously increase the electric field from E1 to E2 with the magnetic field unchanged, a plateau in the MCE curve from T1 to T2 (green line in Figure 3) is obtained, indicating a broad working temperature region.[46] Therefore, with the electric field control of MCE, we can overcome two important hurdles in the application of MCE: reducing the thermal and magnetic irreversibility as well as expanding working temperature window.

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Adv. Mater. 2014, DOI: 10.1002/adma.201404725

www.advmat.de www.MaterialsViews.com

COMMUNICATION Figure 2. The calculated ΔTad for NiCoMnIn ribbon with the magnetic field varying from 0 to 2 T under different electric fields: a) in the heating process, b) in the cooling process. The temperature dependence of ΔS for NiCoMnIn ribbon with the magnetic field varying from 0 to 2 T: c) in the heating process, d) in the cooling process.

In the following section, we will demonstrate that the cooling efficiency can be remarkably improved in the magnetic refrigerator based on the aforementioned effect. It is known that AMR is regarded as an alternative refrigeration cycle with a potential

Figure 3. Schematic image of obtaining MCE with widen operating temperature region. The red and blue curves represent the MCE at fixed electric fields E1 and E2, respectively. A plateau (horizontal solid line) in the MCE curve from T1 to T2 is formed by continuously increasing electric field from E1 to E2 with the magnetic field unchanged. The longer doubleheaded arrow indicates the enlarged operating temperature region.

Adv. Mater. 2014, DOI: 10.1002/adma.201404725

gain of energy efficiency compared to conventional refrigeration techniques.[47] Figure 4a is a schematic image of AMR, which is composed of a hot reservoir, a cold reservoir, and a material bed filling of refrigerants (for example, NiCoMnIn).[48] Typically, a complete AMR operating cycle consists of four stages: (1) magnetization; (2) hot blow; (3) demagnetization; and (4) cold blow. In the initial state, the temperature of refrigerants is T0 and the applied electric field is E0. By applying magnetic field, the temperature of refrigerants decreases to T1 due to the inverse MCE of NiCoMnIn,[35] as shown in Figure 4b. After a hot blow process from the hot reservoir to the cold reservoir, a temperature gradient field between Thot and Tcold is built in the refrigerants,[49] which can be seen from Figure 4c. As a result, some refrigerants may not locate in their optimal working temperature range now (in present case, the ideal working temperature is in the vicinity of T0), leading to the decrease of the cooling efficiency. As mentioned above, the operating temperature of NiCoMnIn alloys can be tuned by applying electric field. Therefore, by altering electric fields, the working temperature of refrigerants can be adjusted to accord with the local temperature, as shown in Figure 4d. Therefore, during the demagnetization process, the refrigerants can now work in their optimal temperature regions and remarkably improve the refrigerating efficiency. The next semi cooling cycle can be operated in the same manner. In conclusion, we investigate the manipulation of electric field on MCE in a NiCoMnIn/PMN-PT laminate. The thermal and magnetic hysteresis of this FSMA can be obviously reduced with the application of electric field. Moreover, the operating

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

wileyonlinelibrary.com

3

www.advmat.de

COMMUNICATION

www.MaterialsViews.com

Figure 4. Schematic image of electric-field-assisted AMR. a) AMR starts at T0. The temperature gradient field is shown in the material bed and the applied electric field is E0. b) Magnetizing process: all the refrigerants are cooled to T1 with the applied magnetic field. At this process, the applied electric field is unchanged. c) The temperature gradient field is built after hot blow process. d) Due to the formation of the temperature gradient field, some refrigerants would locate in Tcold or Thot while their ideal working temperature region is in the vicinity of T0. By applying various electric fields on the refrigerants, the working temperature can be adjusted to accord with the local temperature, which is helpful to increase the cooling efficiency.

temperature window of the sample can be remarkably extended through a multicaloric effect combining magnetocaloric and barocaloric effects. Taking advantage of the electric field control of MCE, the refrigerant NiCoMnIn can be tuned to operate in its optimal working temperature region, which significantly enhances the efficiency of AMR.[46] The electric field control of MCE would have great potential in designing more efficient magnetic refrigerator and improving present magnetic cooling technology.[21,22,44,47,48]

Supporting Information Supporting Information is available from the Wiley Online Library or from the author.

Acknowledgements This work is supported by the National Basic Research Program of China (2014AA032904 and 2012CB932304), and the National Natural Science Foundation of China (Grant Nos. 11174130, 51371095, 51371184, and U1232210).

Experimental Section The NiMnCoIn ribbons are prepared by induction melting the bulk sample in a quartz tube and ejected onto a copper wheel rotating with a surface velocity of 20 m s−1. The as-quenched ribbons are annealed at 900 °C for 15 min in a vacuumed quartz ampoule and then quenched into water. By a scanning electron microscope (SEM) equipped with an X-ray energy dispersive spectroscopy (EDS) system, the average elemental chemical composition of the ribbon is determined as Ni44Co5.2Mn36.7In14.1 while its thickness is estimated to be 22 µm. The -orientated PMN-PT single crystal coated with gold as working electrodes is commercially supplied and polarized in the thickness direction. A piece of annealed ribbon with typical dimensions of 5.5 mm × 3.5 mm is adhered to the substrate with dimensions of 8 mm × 5 mm × 0.5 mm by epoxy (type E-44). A DC voltage is applied on the PMN-PT substrate along the direction of prepolarization with an electrometer (model 2410, Keithley). Magnetic measurements are performed on a refitted superconducting quantum interference device magnetometer, (SQUID, Quantum Design) in which the electric field can be applied in situ with an electrometer. Thermomagnetic measurements are performed under various magnetic and electric fields. The value of Tt is defined as the temperature, where dM/dT is maximum. Isothermal magnetization curves are measured using a so-called loop process to avoid the irreversibility in the magnetic-field-induced first-order magnetostructural transformation.[43] ΔTad and ΔS are calculated by a phenomenological model and Maxwell relation, respectively, which are introduced in detail in the Supporting Information.

4

wileyonlinelibrary.com

Received: October 13, 2014 Revised: November 17, 2014 Published online: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14]

M. Fiebig, J. Phys. D: Appl. Phys. 2005, 38, R123. W. Eerenstein, N. D. Mathur, J. F. Scott, Nature 2006, 442, 759. T. Kimura, Annu. Rev. Mater. Res. 2007, 37, 387. D. Khomskii, Physics 2009, 2, 20. Y. Tokura, S. Seki, Adv. Mater. 2010, 22, 1554. L. Y. Wang, D. H. Wang, Q. Q. Cao, Y. X. Zheng, H. C. Xuan, J. L. Gao, Y. W. Du, Sci. Rep. 2012, 2, 223. N. A. Spaldin, S. W. Cheong, R. Ramesh, Phys. Today 2010, 63, 38. R. Ramesh, N. A. Spaldin, Nat. Mater. 2007, 6, 21. C. A. F. Vaz, J. Phys. Condens. Matter 2012, 24, 333201. C. W. Nan, M. I. Bichurin, S. Dong, D. Viehland, G. Srinivasan, J. Appl. Phys. 2008, 103, 031101. D. Chiba, M. Sawicki, Y. Nishitani, Y. Nakatani, F. Matsukura, H. Ohno, Nature 2008, 455, 515. D. Chiba, M. Yamanouchi, F. Matsukura, H. Ohno, Science 2003, 301, 943. M. Sawicki, D. Chiba, A. Korbecka, Y. Nishitani, J. A. Majewski, F. Matsukura, T. Dietl, H. Ohno, Nat. Phys. 2010, 6, 22. S. M. Wu, S. A. Cybart, P. Yu, M. D. Rossell, J. X. Zhang, R. Ramesh, R. C. Dynes, Nat. Mater. 2010, 9, 756.

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Adv. Mater. 2014, DOI: 10.1002/adma.201404725

www.advmat.de www.MaterialsViews.com

Adv. Mater. 2014, DOI: 10.1002/adma.201404725

COMMUNICATION

[15] S. Zhang, Y. G. Zhao, X. Xiao, Y. Z. Wu, S. Rizwan, L. F. Yang, P. S. Li, J. W. Wang, M. H. Zhu, H. Y. Zhang, X. F. Jin, X. F. Han, Phys. Rev. Lett. 2012, 108, 137203. [16] C. Thiele, K. Dörr, O. Bilani, J. Rödel, L. Schultz, Phys. Rev. B. 2007, 75, 054408. [17] H. C. Xuan, L. Y. Wang, Y. X. Zheng, Y. L. Li, Q. Q. Cao, S. Y. Chen, D. H. Wang, Z. G. Huang, Y. W. Du, Appl. Phys. Lett. 2011, 99, 032509. [18] C. Binek, V. Burobina, Appl. Phys. Lett. 2013, 102, 031915. [19] G. Radaelli, D. Petti, E. Plekhanov, I. Fina, P. Torelli, B. R. Salles, M. Cantoni, C. Rinaldi, D. Gutiérrez, G. Panaccione, M. Varela, S. Picozzi, J. Fontcuberta, R. Bertacco, Nat. Commun. 2014, 5, 3404. [20] Y. T. Yang, Q. M. Zhang, D. H. Wang, Y. Q. Song, L. Y. Wang, L. Y. Lv, Q. Q. Cao, Y. W. Du, Appl. Phys. Lett. 2013, 103, 082404. [21] K. A. Gschneidner Jr., V. K. Pecharsky, Int. J. Refrigeration 2008, 31, 945. [22] A. M. Tishin, J. Magn. Magn. Mater. 2007, 316, 351. [23] M. H. Phan, S. C. Yu, J. Magn. Magn. Mater. 2007, 308, 325. [24] V. K. Pecharsky, K. A. Gschneidner Jr., Phys. Phys. Lett. 1997, 78, 4494. [25] J. D. Moore, K. Morrison, G. K. Perkins, D. L. Schlagel, T. A. Lograsso, K. A. Gschneidner Jr., V. K. Pecharsky, L. F. Cohen, Adv. Mater. 2009, 21, 3780. [26] F. X. Hu, B. G. Shen, J. R. Sun, Z. H. Cheng, G. H. Rao, X. X. Zhang, Appl. Phys. Lett. 2001, 78, 3675. [27] A. Fujita, S. Fujieda, Y. Hasegawa, K. Fukamichi, Phys. Rev. B. 2003, 67, 104416. [28] O. Tegus, E. Brück, K. H. J. Buschow, F. R. de Boer, Nature 2002, 415, 150. [29] S. A. Nikitin, G. Myalikgulyev, A. M. Tishin, M. P. Annaorazov, K. A. Asatryan, A. L. Tyurin, Phys. Lett. A 1990, 148, 363. [30] R. O. Cherifi, V. Ivanovskaya, L. C. Phillips, A. Zobelli, I. C. Infante, E. Jacquet, V. Garcia, S. Fusil, P. R. Briddon, N. Guiblin, A. Mougin, A. A. Ünal, F. Kronast, S. Valencia, B. Dkhil, A. Barthélémy, M. Bibes, Nat. Mater. 2014, 13, 345. [31] X. Moya, L. E. Hueso, F. Maccherozzi, A. I. Tovstolytkin, D. I. Podyalovskii, C. Ducati, L. C. Phillips, M. Ghidini, O. Hovorka, A. Berger, M. E. Vickers, E. Defay, S. S. Dhesi, N. D. Mathur, Nat. Mater. 2013, 12, 53.

[32] T. Krenke, E. Duman, M. Acet, E. F. Wassermann, X. Moya, L. Mañosa, A. Planes. Nat. Mater. 2005, 4, 450. [33] S. Aksoy, T. Krenke, M. Acet, E. F. Wassermann, X. Moya, L. Mañosa, A. Planes, Appl. Phys. Lett. 2007, 91, 241916. [34] A. Planes, L. Mañosa, M. Acet, J. Phys.: Condens. Matter 2009, 21, 233201. [35] J. Liu, T. Gottschall, K. P. Skokov, J. D. Moore, O. Gutfleisch, Nat. Mater. 2012,11, 620. [36] A. M. Aliev, A. B. batdalov, I. K. Kamilov, V. V. Koledov, V. G. Shavrov, V. D. Buchelnikov, J. Garcia, V. M. Prida, B. Hernando, Appl. Phys. Lett. 2010, 97, 212505. [37] L. Mañosa, X. Moya, A. Planes, O. Gutfleisch, J. Lyubina, M. Barrio, J. L. Tamarit, S. Aksoy, T. Krenke, M. Acet, Appl. Phys. Lett. 2008, 92, 012515. [38] S. E. Muthu, N. V. Rama Rao, M. Manivel Raja, S. Arumugam, K. Matsubayasi, Y. Uwatoko, J. Appl. Phys. 2011, 110, 083902. [39] A. K. Nayak, K. G. Suresh, A. K. Nigam, A. A. Coelho, S. Gama, J. Appl. Phys. 2009, 106, 053901. [40] V. V. Khovaylo, K. P. Skokov, O. Gutfleisch, H. Miki, R. Kainuma, T. Kanomata, Appl. Phys. Lett. 2010, 97, 052503. [41] J. Liu, N. Scheerbaum, J. Lyubina, O. Gutfleisch, Appl. Phys. Lett. 2008, 93, 102512. [42] C. Thiele, K. Dörr, S. Fähler, L. Schultz, D. C. Meyer, A. A. Levin, P. Paufler, Appl. Phys. Lett. 2005, 87, 262502. [43] L. Caron, Z. Q. Ou, T. T. Nguyen, D. T. Cam Thanh, O. Tegus, E. Brück, J. Magn. Magn. Mater. 2009, 321, 3559. [44] A. M. Tishin, in Handbook of Magnetic Materials (Ed: K. H. J. Buschow), Vol. 12, Amsterdam, Netherlands, 1999, pp. 295–524. [45] L. Mañosa, D. González-Alonso, A. Planes, E. Bonnot, M. Barrio, J. L. Tamarit, S. Aksoy, M. Acet, Nat. Mater. 2010, 9, 478. [46] N. A. De Oliveira, Appl. Phys. Lett. 2007, 90, 052501. [47] K. K. Nielsen, J. Tusek, K. Engelbrecht, S. Schopfer, A. Kitanovski, C. R. H. Bahl, A. Smith, N. Pryds, A. Poredos, Int. J. Refrigeration 2011, 34, 60. [48] V. K. Pecharsky, K. A. Gschneidner Jr., J. Magn. Magn. Mater. 1999, 200, 44. [49] B. F. Yu, Q. Gao, B. Zhang, X. Z. Meng, Z. Chen, Int. J. Refrigeration 2003, 26, 622.

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

wileyonlinelibrary.com

5

Electric field control of the magnetocaloric effect.

Through strain-mediated magnetoelectric coupling, it is demonstrated that the magnetocaloric effect of a ferromagnetic shape-memory alloy can be contr...
823KB Sizes 0 Downloads 8 Views