2005/01/31 by M. Goiran, M Goiran, M Costes +15
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Copper-based nanomaterials and applications #Physics of Superconductivity and Magnetism #cond-mat.str-el
paper · pdf · doi:10.1088/1367-2630/8/5/074
revised version, accepted for publication in the New Journal of Physics
arxiv created 2006/04/24 · openalex publication_date 2006/05/25 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/30
We report an electron spin resonance (ESR) study of the s = 1/2 Heisenberg pseudo-ladder magnet CaCu 2 O 3 in pulsed magnetic fields up to 40 T. At sub-terahertz frequencies we observe an ESR signal originating from a small amount of uncompensated spins residing presumably at the imperfections of the strongly antiferromagnetically correlated host spin lattice. The data give evidence that these few per cent of 'extra' spin states are coupled strongly to the bulk spins and are involved in the antiferromagnetic (AF) ordering at T N = 25 K. By mapping the frequency/resonance field diagram we have determined a small gap for magnetic excitations below T N of the order of ∼0.3–0.8 meV. Such a small value of the gap explains the occurrence of the spin-flop transition in CaCu 2 O 3 at weak magnetic fields μ 0 H sf ∼ 3 T. Qualitative changes of the ESR response with the increasing field strength give indications that strong magnetic fields reduce the AF correlations and may even suppress the long-range magnetic order in CaCu 2 O 3 . ESR data support scenarios with a significant role of the 'extra' spin states for the properties of low-dimensional quantum magnets.