Perturbed-angular-correlation studies in hafnium doped La0.67Ca0.33MnO3

Competing magnetic phases in La0.7Sr0.3MnO3as deduced from Mn site hyperfine parameters

“…However, a detailed picture involving the changes in both the MHF and EFG of the coexisting phases and hence the complete atomic scale understanding of these phases is yet to emerge. Using time differential perturbed angular correlation (TDPAC), a hyperfine interaction technique with 181 Hf/Ta probe, it has been shown that Hf substitutes Mn sites in undoped [14,15] and Ca/Sr doped LaMnO 3 [16,17]. The MHF as perceived by the probe nucleus (Ta) occupying Mn sites is due to the transfer of spin density from magnetically ordered Mn d orbitals through O p orbitals on to primarily the 4s and 5s orbitals of the probe ion, namely the super transferred hyperfine field (STHF).…”

“…This work also illustrates a linear correlation between EFG and MHF as experienced by probe atoms occupying Mn 3+ and Mn 4+ rich sites with the slope being dictated by the nature of local magnetic ordering. La 0.7 Sr 0.3 Mn 0.995 Hf 0.005 O 3 (LSMO) samples were prepared by the standard solid state reaction method described elsewhere [16] and characterized by x-ray diffraction to be of single phase with rhombohedral structure having lattice parameters a = 5.5032 Å and c = 13.375 Å. These samples were neutron irradiated at the DHRUVA reactor, BARC, Mumbai, to produce the probe nuclei by the reaction 180 Hf(n, γ ) 181 Hf(β − ) 181 Ta.…”

“…is evaluated [16], and this contains information on the hyperfine interaction parameters. This anisotropy function R(t) is analysed to extract the quadrupole and magnetic hyperfine parameters: the Larmor frequency is given as ω L = gµ N B hf / h where g is the nuclear gyromagnetic factor and B hf is the MHF.…”

“…The occurrence of such Mn 3+ rich and Mn 4+ rich zones have been identified in LCMO based on PAC studies related to oxygen stoichiometric effects. The existence of the two components in LSMO/LCMO has earlier been attributed to the intrinsic chemical inhomogeneity [16,17,19] at the nanoscale arising due to Sr/Ca doping and the concomitant distribution of Mn 4+ ions. Appreciable dampening of the spectra is mainly understood to be due to electronic inhomogeneity caused by the doping of Sr or Ca in these systems as discussed earlier [16].…”

“…The existence of the two components in LSMO/LCMO has earlier been attributed to the intrinsic chemical inhomogeneity [16,17,19] at the nanoscale arising due to Sr/Ca doping and the concomitant distribution of Mn 4+ ions. Appreciable dampening of the spectra is mainly understood to be due to electronic inhomogeneity caused by the doping of Sr or Ca in these systems as discussed earlier [16]. The dampening parameter is significantly dependent upon cationic (La, Sr) and anionic (oxygen) concentration and distribution.…”