Magnetization steps due to pairs of distant-neighbor spins in Zn1-xCoxSe and Zn1-xCoxS

Abstract

Magnetization steps (MSTs) were observed in Zn1-xCoxSe and Zn1-xCoxS using temperatures T < 1 K, steady magnetic fields up to 200 kOe, and pulsed fields up to ∼400 kOe. Unlike the MSTs observed earlier in other materials, these MSTs are due to pairs of distant-neighbor spins rather than to pairs of nearest-neighbor spins. For Zn1-xCoxSe the results give a second-neighbor exchange constant J2/kB = −3.04±0.1 K, and suggest a third-neighbor exchange constant J3/kB ≌ −0.8 K. An exchange constant J/kB = −2.25±0.2 K observed in Zn1-xCoxS is either J2 or J3.