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Journal Articles

Occupation sites and valence states of Co dopants in (La, Co)-codoped M-type Sr ferrite; $$^{57}$$Fe and $$^{59}$$Co nuclear magnetic resonance studies

Sakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Ueda, Hiroaki*; Tanioku, Yasuaki*; Michioka, Chishiro*; Yoshimura, Kazuyoshi*; Takao, Kenta*; Shimoda, Aiko*; et al.

Physical Review B, 98(6), p.064403_1 - 064403_10, 2018/08

 Times Cited Count:10 Percentile:46.45(Materials Science, Multidisciplinary)

To specify preferential occupation sites of Co substituents and to clarify charge and spin states of Co ions in (La, Co)-cosubstituted hexagonal magnetoplumbite-type (M-type) Sr ferrite, $$^{57}$$Fe and $$^{59}$$Co nuclear magnetic resonance (NMR) spectra are measured under zero and external magnetic fields using powdered and single crystalline specimens. To a considerable degree, the charge compensation between La$$^{3+}$$ and Co$$^{2+}$$ works in the equal (La, Co)-codoped case, where more than half of the Co ions are considered to be present in the minority spin $$4f_1$$ sites at the center of the oxygen tetrahedra, with the $$S$$ = 3/2 state carrying a small orbital moment owing to spin-orbit interaction. The remaining small number of high-spin Co$$^{2+}$$ ($$S$$ = 3/2, $$L$$ = 1) ions with unquenched orbital moments would be distributed to the other octahedral $$12k$$, $$2a$$, and $$4f_2$$ sites.

Oral presentation

$$^{57}$$Fe NMR study in La-Co substituted M-type Sr ferrite

Sakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Shimoda, Aiko*; Waki, Takeshi*; Tabata, Yoshikazu*; Nakamura, Hiroyuki*

no journal, , 

Zero field NMR experiments on SrFe$$_{12}$$O$$_{19}$$ and Sr$$_{1-x}$$La$$_{x}$$Fe$$_{12-x}$$Co$$_{x}$$O$$_{19}$$ have been performed. The substitued Co sites will be discussed based on the NMR spectra.

Oral presentation

$$^{59}$$Co NMR study in La-Co substituted $$M$$-type Sr Ferrite

Sakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Shimoda, Aiko*; Waki, Takeshi*; Tabata, Yoshikazu*; Nakamura, Hiroyuki*

no journal, , 

Zero field NMR experiments have been done using powdered samples and single crystals of SrFe$$_{12}$$O$$_{19}$$ and La-Co co-substituted Sr$$_{1-x}$$La$$_x$$Fe$$_{12-x}$$Co$$_{x}$$O$$_{19}$$. The single crystals were grown by the flux method. $$^{59}$$Co NMR signals have been observed in the lower frequency range of 50-100 MHz and in the higher frequency range of 300-400 MHz. Spectral intensity in the lower frequency range is stronger than that in the higher frequency range. We will discuss the spin and charge states of Co ions using the NMR results, some complementary experiments and theoretical considerations.

Oral presentation

NMR study in La-Co substituted M-type Sr Ferrite

Sakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Shimoda, Aiko*; Waki, Takeshi*; Tabata, Yoshikazu*; Nakamura, Hiroyuki*

no journal, , 

$$^{57}$$Fe and $$^{59}$$Co NMR spectra have been observed for La-Co co-substituted M-type Ferrite. We will microscopically discuss about the Co sites in the co-substituted M-type Ferrite as well as spin and charge states of Co ions.

Oral presentation

$$^{57}$$Fe, $$^{59}$$Co-NMR study in La-Co substituted M-type Sr ferrite

Sakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Shimoda, Aiko*; Waki, Takeshi*; Tabata, Yoshikazu*; Nakamura, Hiroyuki*

no journal, , 

We will discuss about the Co sites and the electronic states of Co ions in La-Co co-substituted SrFe$$_{12}$$O$$_{19}$$ using the $$^{57}$$Fe and $$^{59}$$Co NMR results.

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