LAUSR

Nanometer scale is introduced in the well-known Haldane system $$\hbox {Y}_{2}\hbox {BaNiO}_{5}\,(S=1)$$Y2BaNiO5(S=1). Magnetization and pulsed-field electron spin resonance (ESR) measurements were performed. As a result, the magnetization of nanoparticles is much enhanced as compared with that of the bulk material. The Haldane gap in the bulk form tends to be suppressed as the grain size is reduced down to the nanometer scale. The chain-end $$S\hbox {-}1/2$$S-1/2 spins have an important contribution to the magnetism of nanoparticles. The high-field ESR data demonstrated a paramagnetic-like resonance. The frequency–field (f–H) relationship is linear and passes through the origin. The g value is about 2.16, in good agreement with the typical value of paramagnetic $$\hbox {Ni}^{2+}$$Ni2+. It is concluded that the nanometer scale is a new degree of freedom for controlling the ground state of quantum magnets.