MAPON efg result of 54Mn in cubic cobalt

Full text: The high resolution spectroscopy, Modulated Adiabatic Passage on Oriented Nuclei (MAPON), provides precise quantifiable mode values for the very small electric field gradient (efg) present at substitutional 3d impurities in crystallographic cubic ferromagnets, Fe, Ni and fcc Co. In conjunction with the much older technique of Adiabatic Fast Passage NMR on oriented nuclei, signs of the efg may be readily determined, leading to increasingly well-defined efg systematics as nuclear quadrupole moments improve in reliability in both sign and magnitude through calculation and experiment. For 3d impurities the efg mode values are, in general, an order of magnitude smaller than those found for 5d impurities in like hosts but are, nevertheless, over an order of magnitude larger than that assigned to distant point defects in undeformed non-magnetic cubic hosts. It has been argued previously that for the 3d probe the dominant mechanism for the efg is distinct from those of the other two categories, being probe intrinsic for a given host, but strongly host dependent for a given probe. In particular, and in contrast to 5d impurities such as Ir, there are efg sign changes depending on whether the ferromagnetic host is either bcc or fcc. From the systematics in hand, it was apparent that Mn in fcc Co should be the same sign efg as Mn in fcc Ni and much the same magnitude. In this paper we present a new MAPON result for the 54Mn (I = 3+, t1/2 = 312 d) probe in polycrystalline, predominantly fcc, cobalt foils which is entirely consistent in sign and magnitude with this empirical prediction. We obtain, using Q= +0.33(3) b, an efg for MnCo (fcc) of Vzz = +1.25(17) x1019Vm-2