NQR and NMR of¹³⁹La in Antiferromagnetic La₂CuO_4-δ

Comment on ‘‘Magnetization and spin-wave velocities inLa2CuO4’’

“…At each temperature up to about 230 K, all the 57 Fe probes experience common hyperfine fields. The normalized thermal variation follows that previously reported from 57 Fe Mossbauer/muon [9] and from 139 La NQR [4,10] measurements. As the temperature is increased above about 230 K, fractions of the probes progressively cross over into the nonmagnetic state so evidencing the inhomogeneity in 7V Figure 1 shows (top) the thermal evolution of the percentage of the 57 Fe probes which experience hyperfine fields (the remainder experience no measurable hyperfine fields) and (bottom) the thermal evolution of the size of the hyperfine field of the fraction of the probes which experience hyperfine fields.…”

Magnetic phase diagram of lightly dopedLa2−xSrChou1, Borsa2, Cho3 et al. 1993Phys. Rev. Lett.166251100View full textAdd to dashboardCite

“…Below T N , the 139 La NQR splits into a doublet at frequencies vi and V2 whose separation Av [see Fig. 1(c)] measures the component H z =Hcos0 of the static effective local internal magnetic field H at the La site parallel to the principal (z) axis of the electric field gradient (EFG) tensor; 0 = 7$° in La2CuC>4 and the z axis is nearly perpendicular to the CuC>2 planes [9]. The two NQR resonance frequencies in the doublet are given by v\ t 2 = 2vQ ± (y/v/2x)H z , where the quadrupole frequency VQ~6.…”

Saylor and Hohenemser reply

“…With this sensitivity they see no increase in the linewidth and no change in the average electric-field-gradient asymmetry parameter 77, in the neighborhood of 150 K. In fact, 77 is zero everywhere within the sensitivity of their measurement [2]. Previous NQR studies, albeit on samples with less well-defined oxygen content, broader lines, and lower T N , also find no temperature dependence in the inhomogeneous linewidth [3][4][5][6].…”