Phonon anomalies versus magnetic ordering in CuO

• Published in: Physica. B, Condensed matter Vol. 284; pp. 1396 - 1397
• Main Authors: Kuz'menko, A.B, van der Marel, D, van Bentum, P.J.M, Tishchenko, E.A, Presura, C, Bush, A.A
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-07-2000
• Subjects: Charge disproportionation; Infrared spectroscopy; Magnetic ordering; Spin–phonon interaction; Infrared spectroscopy; Charge disproportionation; Spin–phonon interaction; Magnetic ordering
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/S0921-4526(99)02557-0

We report the first measurements of FIR and MIR reflectivity of single-crystal monoclinic antiferromagnetic copper monoxide (CuO) in a wide temperature range (7–300 K) when
b
-axis and
ac
-plane polarized modes are completely separated and excited in transverse geometry. Previously reported softening of the A
u
3 mode at the Néel transition is confirmed and found to be up to two times more significant (about 10%). For the first time an emergence of several new IR-active lines at low temperatures is observed. The highest frequency new mode at
690
cm
−1
strongly hardens and strengthens with cooling. The data are discussed in terms of strong spin–phonon coupling and possible charge disproportionation at low
T.