Anomalous magnetocaloric effect and magnetoresistance inHo(Ni,Fe)2compounds

Abstract

Magnetic, magnetocaloric, and magnetoresistance studies have been carried out on polycrystalline samples of Laves phase compounds Ho͑Ni 1−x Fe x ͒ 2 ͓x = 0, 0.05, and 0.1͔. The magnetocaloric effect in HoNi 2 is found to be maximum near the ordering temperature with values of 7 J mol −1 K −1 and 10.1 K for the isothermal magnetic entropy change and the adiabatic temperature change, respectively, for a field of 50 kOe. With Fe substitution, the temperature variation of magnetocaloric effect shows an additional peak at low temperatures, which is much more pronounced than the peak at the ordering temperature. The origin of the low temperature peak is attributed to the field-induced metamagnetic transition. The magnetoresistance data also seem to support the occurrence of the metamagnetic transition.

Effect of Ge substitution for Si on the anomalous magnetocaloric and magnetoresistance properties of GdMn2Si2 compounds

“…The MCE behavior seen in this compound is similar to that of Ho͑Ni, Fe͒ 2 compounds. 24 The maximum values of ⌬S M ͑⌬S M max ͒ for GdMn 2 SiGe and GdMn 2 Ge 2 are found to be 6.3 and 5.9 J / kg K at about 57 and 96 K, respectively. It is also evident from Figs.…”

“…This has been done using the methods reported earlier. 16,23,24 Figures 8͑a͒-8͑c͒ show the temperature variation of ⌬S M and ⌬T ad for a field change ͑⌬H͒ of 50 kOe, for all compounds. ⌬S M values calculated from the C-H-T data were found to be in close agreement with those obtained from the M-H-T data.…”

Effect of magnetic polarons on the magnetic, magnetocaloric, and magnetoresistance properties of the intermetallic compound HoNiAl

“…[1][2][3] The possibility of magnetic refrigeration emerging as an alternative to the conventional gas compression methods has led to an intensive research, both on experimental as well as on theoretical aspects, in the field of MCE. [4][5][6] Generally, the MCE is measured in terms of isothermal magnetic entropy change or adiabatic temperature change and the materials with significant MCE over a wide temperature range are being considered as the active elements in a magnetic refrigerator.…”

About the Role of Fe-Ions in the Formation of Magnetocaloric Effect in Ho(Co1-xFex)2Compounds

“…The inset II shows the values of ∆T FWHM for R(M 1−x Fe x ) 2 compounds, where M = Co or Ni. Data have been taken from the papers [9][10][11][12]15] and from the present stady. The gure shows that for all R(M 1−x Fe x ) 2 compounds with low Ni or Co substitutions by Fe, a signicant increase of ∆S(T ) peak width is observed.…”

“…Recently, the study of Ho(Ni 1−x Fe x ) 2 quasibinary system revealed that the nickel substitution by iron leads to abnormal MCE [9]. This anomaly manifested as MCE presence in much wider temperature range, contrary to the many known magnetocaloric materials.…”