The search for magnetic order in [formula omitted]-Pu metal using muon spin relaxation

Abstract

We review results from previous muon spin relaxation ( μ SR) measurements in applied fields of H 0 = 0 and 0.25 T which established an upper limit for the ordered or disordered frozen spin moment above T = 4 K in δ -Pu (4.3 at.% Ga) of μ ord ≤ 1 0 − 3 μ B . In addition, we present new data in H 0 = 0.25 and 2 T applied field on a highly annealed δ -Pu (4.3 at.% Ga) sample. Neither the muon Knight shift ( H 0 = 2 T) nor the inhomogeneous linewidths in the new sample show appreciable temperature dependence below about T = 60 K, also consistent with no spin freezing. Recent theoretical arguments advanced to explain these results are mentioned.