Nuclear secondary echo in ferromagnets caused by quadrupole and Suhl–Nakamura interactions

Abstract

The formation of the secondary nuclear spin echo signals in ferromagnets has been investigated taking into consideration the quadrupole and Suhl–Nakamura interactions. It is assumed that the inhomogeneous distribution of the quadrupole frequency ωQ+δωQ is independent of the distribution of nuclear magnetic resonance frequency ωn+δωn, and a characteristic size of these inhomogeneities is small in comparison to the correlation radius of the exchange interaction in the electron ferromagnetic system. It is shown that the quadrupole interaction causes the formation of the secondary echo signals at t=(2k+1)τ, 1≤k≤I−1/2, where I is the nuclear spin, the time t is measured from the second rf pulse, and τ is the time interval between the rf pulses. The spectrum of the spin echo signal with maximum at t=tE contains (2I+1−tE/τ) frequencies. The Suhl–Nakamura interaction causes the additional echo signals with maximum at even values t/τ.