Supplementary materials

Magnetostructural coupling and magnetocaloric effect in Ni-Mn-Ga-Cu microwires

Xuexi Zhang, Mingfang Qian, Zhe Zhang, Longsha Wei, Lin Geng, Jianfei Sun

School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China

FIG. S1. A macro-photograph showing the morphology of Ni-Mn-Ga-Cu microwires prepared by a modifiedmelt-extraction machine in our lab. Large quantities of the microwire may be prepared by this technique.

FIG. S2.Room temperature X-ray diffraction (XRD) patterns of the parent ingot (bottom), as-extracted (middle) and annealed (top) microwires. The XRD measurements were performed on a Rigaku D/max-γA X-ray diffractometer with Cu Kα radiation (λ = 1.54 Å). For the as-extracted and annealed microwires, a bunch of parallel microwires were placed on a monocrystalline silicon wafer for XRD measurement in order to increase the diffraction intensity and facilitate the operation. The XRD patterns show that the parent ingot and both of the microwires are single-phase alloys containing seven-layer modulated (7M) martensite phase. By the whole pattern fitting analysis, the 7M martensite was determined to be a monoclinic incommensurate superstructure (L. Righi, et al., Acta Mater. 56 (2008) 4529–4535) with the crystal lattice constants a = 4.28 Å, b = 5.49 Å, c = 42.23 Å,  = 92.5º for the ingot, a = 4.25 Å, b = 5.52 Å, c = 42.22 Å,  = 93.3º for the as-extracted microwiresanda = 4.25 Å, b = 5.52 Å, c = 42.10 Å, = 93.5º for the annealed microwires.

FIG. S3. Heating and cooling DSC curves (upper) and M-T curves at 0.2 kOe (lower) of the as-extracted Ni-Mn-Ga-Cu microwires. The as-extracted microwires exhibitsmall magnetization due to the low degree of atomic orderingformed during the rapid solidification.

TABLE SI.The maximum entropy change ΔSm, full width at half maximumFWHM and refrigeration capacity RC values of the present Ni-Mn-Ga-Cu microwire and some other compounds with giant MCE.

Materials / 20 kOe / 50 kOe
ΔSm
(J/kgK) / FWHM
(K) / RC
(J/kg) / ΔSm
(J/kgK) / FWHM
(K) / RC
(J/kg)
Present Ni-Mn-Ga-Cu microwire / ~3.6 / ~12
(351.5-363.5) / 33.1i (43.2ii) / ~8.3 / ~13
(351.4-364.4) / 78.0i (107.8ii)
Ni52Mn26Ga22 (R) / ~16.4 / ~2 (353-355) / 32ii / ~30 / ~2.5
(353-355.5) / 70ii / [a]
Ni43Mn46Sn11 (R) / - / - / - / ~41.4 / ~6.3
(210.5-216.8) / 115.4i / [b]
LaFe11.8Si1.2 (R) / - / - / - / ~31 / ~21(192-213) / - / [c]
Ni2Mn0.75Cu0.25Ga (B) / 17.2 / ~2.7
(312.5-315.2) / 47ii / - / - / - / [d]
Ni2Mn0.75Cu0.25Ga (B) / - / - / - / 65 / ~1.7
(307.3-309) / 72i / [e]
Ni2.15Mn0.8Cu0.05Ga (B) / 14.9 / ~3(329-332) / 44.7ii / - / - / - / [f]
Ni21.5Mn0.78Cu0.07Ga (B) / 21.7 / ~2
(338.5-340.5) / 43.4ii / - / - / - / [f]
Ni51 Mn20Cu4Ga25 (B) / - / - / - / ~18.2 / ~5(301-306) / 75i / [g]
Ni55.4Mn20.0Ga24.6 (B) / 86 / ~0.9
(312.3-313.2) / 77.4ii / [h]
Ni55.2Mn18.6Ga26.2 (B) / 20.4 / ~5
(314.8-319.8) / 102ii / [i]
Ni55Mn19.6Ga25.4 (B) / 10.4 / 3.5(307.5-311) / 45.5i / - / - / - / [j]
Ni2.29Mn0.89Ga0.82 (B) / 20 / ~6.5
(316-322.5) / 100i / [k]
Ni54.3Mn20.1Ga25.6 (B) / 7.3 / - / 17i / - / - / - / [l]
Gd (B) / 10.6 / ~70(260-330) / - / [m]

i--ii-- RC=ΔSm×FWHM

R--Ribbons; B--Bulk polycrystalline or monocrystalline alloys.

[a] Applied Physics Letters, 104 (2014) 044101; [b] Scientific Reports, 5 (2015) 11010; [c] Journal of Applied Physics, 97 (2005) 10M305; [d] Journal of Applied Physics, 99 (2006) 08Q106; [e] Applied Physics Letters, 88 (2006) 192511; [f] Journal of Applied Physics, 103 (2008); [g] Journal of Alloys and Compounds, 630 (2015) 244-249; [h] Physical Review B, 72 (2005); [i] Journal of Applied Physics, 97 (2005) 10M515; [j] Journal of Alloys and Compounds, 478 (2009) 59-62; [k] Solid State Communications, 152 (2012) 372-374; [l] Journal of Applied Physics, 111 (2012) 07A933; [m] Physical Review B, 57 (1998) 3478-3490.