Muon-spin relaxation study of the spin-(1)(2) molecular chain compound Cu(HCO2)(2)(C4H4N2)

We present the results of a muon-spin relaxation (μ+ SR) study of magnetic order in the quasi-one-dimensional spin-1/2 molecular chain compound Cu (HCO2) 2 (C4 H4 N2). Zero-field μ+ SR measurements at low temperatures show oscillations in the measured asymmetry, characteristic of a quasistatic magnetic field at the muon sites. Our measurements provide convincing evidence for long-range magnetic order below a temperature TN =1.97(8) K. This leads to an estimate of the interchain coupling constant of J′ /kB =1.27 K and to a ratio J′ /J=1.6× 10-1. © 2006 The American Physical Society