For the spin-chain compound ${\mathrm{Ca}}_3{\mathrm{Co}}_2{\mathrm{O}}_6$, the magnetization curves as a function of the magnetic field are strongly out-of-equilibrium at low temperature, and they exhibit several steps whose origins are still a matter for debate. In the present paper we report on a detailed investigation of the temperature and time dependence of these features. First, it is found that some of the magnetization steps can disappear as the characteristic time of the measurement is increased. A comparison of the influence of temperature and time points to the existence of a thermally activated process that plays an important role in determining the form of the magnetization curves. Second, direct investigations of the magnetic response as a function of time show that this thermally activated process competes with a second relaxation mechanism of a very different nature, which becomes dominant at the lowest temperatures. These results shed new light on the peculiar magnetization process of this geometrically frustrated, Ising-like spin-chain compound.

• Received 7 January 2004

DOI:https://doi.org/10.1103/PhysRevB.70.064424