Diagonal Antiferromagnetic Easy Axis in Lightly Hole Doped Y_{1-x}Ca_xBa_2Cu_3O_6

TL;DR

This study investigates how light hole doping affects the antiferromagnetic structure and magnetic anisotropy in a copper oxide crystal, revealing a temperature-dependent easy axis transition likely due to hole ordering.

Contribution

It demonstrates a temperature-dependent change in magnetic easy axis in lightly hole-doped cuprates, suggesting hole ordering influences magnetic anisotropy.

Findings

Easy axis shifts from [110] to [100] with increasing temperature.

Holes do not localize to Ca2+ ions above 2.5 K.

Magnetic domain structure depends on external magnetic field.

Abstract

Hole induced changes in the antiferromagnetic structure of a lightly Ca doped Gd:Y_{1-x}Ca_xBa_2Cu_3O_6 copper oxide single crystal with x~0.008 is investigated by Gd3+ electron spin resonance. Holes do not localize to Ca2+ ions above 2.5 K since the charge distribution and spin susceptibility next to the Ca2+ are independent of temperature. Both hole doped and pristine crystals are magnetically twinned with an external magnetic field dependent antiferromagnetic domain structure. Unlike the undoped crystal, where the easy magnetic axis is along [100] at all temperatures, the easy direction in the hole doped crystal is along the [110] diagonal at low temperatures and changes gradually to the [100] direction between 10 K and 100 K. The transition is tentatively attributed to a magnetic anisotropy introduced by hole ordering.