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Title: Magnetostructural phase transitions and magnetocaloric effect in (Gd 5-xSc x)Si 1.8Ge 2.2

Future advancements in magnetocaloric refrigeration/heat pumping technologies depend on the discovery of new materials that demonstrate large, tunable magnetocaloric effects (MCEs) in the vicinity of coupled magnetic and structural phase transitions that occur reversibly with minimum hysteresis. Here, with this in mind, we investigate phase transitions, microstructure, magnetic, thermal, magnetocaloric, and transport properties of (Gd 5-xSc x)Si 1.8Ge 2.2 compounds. Replacement of magnetic Gd with non-magnetic Sc in Gd 5-xSc xSi 1.8Ge 2.2 increases the ferromagnetic to paramagnetic first order phase transition temperature, T C, with only a minor reduction in MCE when x ≤ 0.2. We also demonstrate that hydrostatic pressure further increases T C and reduces the hysteresis of the first order phase transition in Gd 4.8Sc 0.2Si 1.8Ge 2.2 from 7 to 4 K. Temperature-dependent x-ray powder diffraction study of Gd 4.8Sc 0.2Si 1.8Ge 2.2 confirms the monoclinic ↔ orthorhombic structural transformation at T C, in agreement with magnetic, calorimetric, and electrical transport measurements. In addition to the substantial magnetocaloric effect, a large magnetoresistance of ~20% is also observed in Gd 4.8Sc 0.2Si 1.8Ge 2.2 for ΔH = 50 kOe in the vicinity of the magnetostructural transition. Finally, in a drastic reversal of the initial doping behaviormore » further additions of Sc (x > 0.2) suppress formation of the monoclinic phase, change the nature of the transition from first-to second-order, and reduce both the transition temperature and magnetocaloric effect.« less
 [1] ;  [2] ;  [2] ;  [3]
  1. Ames Lab. and Iowa State Univ., Ames, IA (United States); Iowa State Univ., Ames, IA (United States). Dept. of Mechanical Engineering
  2. Ames Lab. and Iowa State Univ., Ames, IA (United States)
  3. Ames Lab. and Iowa State Univ., Ames, IA (United States); Iowa State Univ., Ames, IA (United States). Dept. of Materials Science and Engineering
Publication Date:
Report Number(s):
Journal ID: ISSN 1359-6454; PII: S1359645417310297; TRN: US1800852
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 145; Journal Issue: C; Journal ID: ISSN 1359-6454
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
36 MATERIALS SCIENCE; Structural transition; Magnetoresistance; Magnetocaloric
OSTI Identifier: