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The Invar Property of Elemental F.C.C. Co and Large Spontaneous Magnetostriction of B.C.C. Fe–Co
Author(s) -
Gehrmann B.,
Acet M.,
Herper H. C.,
Wassermann E. F.,
Pepperhoff W.
Publication year - 1999
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/(sici)1521-3951(199907)214:1<175::aid-pssb175>3.0.co;2-j
Subject(s) - invar , magnetostriction , materials science , thermal expansion , ferromagnetism , condensed matter physics , crystallography , metallurgy , chemistry , magnetic field , physics , quantum mechanics
The ferromagnetic invar effect in f.c.c. 3d‐transition metal alloys spans an (s+d) valence electron concentration range of 8.6 ≤ e / a ≤ 9.5. The maximum spontaneous magnetostriction associated with the invar effect occurs at e / a ≈ 8.7. For e / a ≤ 8.6, the anti‐invar effect develops, for which the associated volume enhancement increases as the pure f.c.c. Fe composition of e / a = 8 is approached. The progressive change from anti‐invar to invar in Fe 1— x Ni x alloys takes place in the range of 0 ≤ x ≤ 0.6 (8 ≤ e / a ≤ 9.2). The electron concentration of Fe 1— x Co x alloys falls within this range with 8 ≤ e / a ≤ 9, implying that Co should be an element having invar properties. To verify this assessment we examine, by thermal expansion measurements in the temperature range of 4 K ≤ T ≤ 1500 K, the volumetric properties of Fe x Co 1— x alloys with 0 ≤ x ≤ 1. Indeed, we find invar behavior in the f.c.c. phase of the alloys with concentrations ranging from x = 0.6 to pure Co. Aside from the invar property of pure f.c.c. Co, we observe features associated with the order–disorder transition (B2 ↔ b.c.c.) and a large magnetostriction in the b.c.c. phase related to magnetic ordering.