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Symmetry‐Breaking Transitions in HoCuAs 2–x P x and ErCuAs 2–x P x (x = 0–2): Crystal Structure, Application of Landau Theory, Magnetic and Electrical Properties
Author(s) -
Mozharivsky Yurij,
Kaczorowski Dariusz,
Franzen Hugo F.
Publication year - 2001
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/1521-3749(200109)627:9<2163::aid-zaac2163>3.0.co;2-n
Subject(s) - monoclinic crystal system , orthorhombic crystal system , tetragonal crystal system , crystallography , crystal structure , condensed matter physics , landau theory , electrical resistivity and conductivity , chemistry , materials science , physics , phase transition , quantum mechanics
Crystal structures of compounds undergoing symmetry‐breaking transitions have been investigated by the X‐ray single crystal and powder methods. While the phases HoCuAs 2 through HoCuAs 1.33 P 0.67 and ErCuAs 2 through ErCuAsP retain the tetragonal HfCuSi 2 structure ( P 4/ nmm space group), the compounds HoCuAsP through HoCuAs 0.33 P 1.67 and ErCuAs 0.67 P 1.33 through ErCuAs 0.33 P 1.67 undergo orthorhombic distortions to the GdCuAs 1.15 P 0.85 structure ( Pmmn space group). Further distortions follow in the phosphides: HoCuP 2 adopts a larger orthorhombic cell ( Cmma , a = 5.273(3), b = 5.305(3), c = 9.645(5) Å) and ErCuP 2 has a monoclinic cell with a doubled parameter, the b parameter in the monoclinic cell ( P 2 1 / n , a = 3.737(3), b = 19.239(15), c = 3.728(3) Å, β = 90.09(1)°). Zigzag chains are formed in the phosphorus layer of ErCuP 2 . According to Landau theory the transitions from HoCuAs 1.33 P 0.67 to HoCuAsP and from ErCuAsP to ErCuAs 0.67 P 1.33 can be continuous, and the transitions from HoCuAs 0.33 P 1.67 to HoCuP 2 and from ErCuAs 0.33 P 1.67 to ErCuP 2 are necessarily first‐order. The results of magnetic and electrical measurements for HoCuAs 2 and HoCuP 2 are reported. Due to the magnetic moments localized on Ho atoms both compounds order antiferromagnetically at low temperatures. They exhibit metallic conductivity.