Spin-Orbit Electric Field Gradient in Cubic Ferromagnets: Strong Magnetization-Direction Dependence of the Field Gradient Distribution

The ISOLDE Collaboration CERN, CH-1211 Geneva 23, Switzerland (Received 19 March 1998; revised manuscript received 19 October 1998) The electric quadrupole interaction of 191Pt (I ­ 3y2; T1y2 ­ 2.9 d) in an Fe single crystal was measured for magnetization M parallel to the crystallographic [100], [110], and [111] axes. For M k f111g and [110] the distribution of the electric field gradient (EFG) is relatively sharp. For M k f100g the EFG distribution is by a factor of 2.8(6) broader than for M k f111g. Additional data on Os, Re, Ir, and Au in Fe indicate that this behavior seems to be of general nature: In all cases the EFG distribution for M k f100g is considerably broader than for M k f110g and [111]. [S0031-9007(98)08187-3]