Takeshi Hanawa

The University of Tokyo

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Technical Report of ISSP Ser. A: Number 2776

Takeshi Hanawa Kotaro Shinkawa Masayasu Ishikawa Kazuo Miyatani Kazuhiro Saito

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Anisotropic Specific Heat of CoNb₂O₆in Magnetic Fields

Journal of the Physical Society of Japan (1994)

Takeshi Hanawa Kohtaro Shinkawa Masayasu Ishikawa Kazuo Miyatani Kazuhiro Saito

We investigated the successive magnetic phase transitions of CoNb 2 O 6 at 2.9 K and 1.9 K by measuring the specific heat, magnetic susceptibility and magnetization of poly- and single-crystalline samples. The specific heat measurements performed in external magnetic fields up to about 1.5 kOe disclosed the Ising-like nature of the transitions and tremendous anisotropic magnetic-field dependence due to the low-dimensional character. Moreover, the specific heat and ac magnetic susceptibility data imply another magnetic state below 1 K. These consequences suggest a very interesting magnetic phase diagram, resulting from the competing single-ion anisotropy and exchange interactions in this compound.

Specific heat

10.1143/jpsj.63.2706

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Disappearance of Ferromagnetism at Low Temperatures in CoNb₂O₆

Journal of the Physical Society of Japan (1992)

Takeshi Hanawa Masayasu Ishikawa Kazuo Miyatani

Specific heat, magnetic susceptibility, and M - H measurements of CoNb 2 O 6 revealed that the compound exhibits two successive phase transitions at 2.9 K (= T 1 ) and 1.9 K (= T 2 ): at T 1 , long-range ferromagnetic order sets in, but below T 2 , the ferromagnetism vanishes and recovers in applied fields higher than about 500 Oe.

Specific heat

Atmospheric temperature range

10.1143/jpsj.61.4287

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Technical Report of ISSP Ser. A: Number 2827

Setsuo Mitsuda Kazuhiro Hosoya Tsuyoshi Wada H. Yoshizawa Takeshi Hanawa

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Competition between the inter-chain interaction and single-ion anisotropy in CoNb2O6

Physica B Condensed Matter (1995)

Satoru Kobayashi Setsuo Mitsuda K. Hosoya H. Yoshizawa Takeshi Hanawa

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Single chain

10.1016/0921-4526(95)00096-r

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Magnetic Ordering in One-Dimensional System CoNb₂O₆with Competing Interchain Interactions

Journal of the Physical Society of Japan (1994)

Setsuo Mitsuda K. Hosoya Tsuyoshi Wada H. Yoshizawa Takeshi Hanawa

We investigated the formation of three-dimensional (3D) magnetic ordering in a quasi-1D ferromagnetic chain system CoNb 2 O 6 by neutron scattering. With decreasing temperature below T 1 ∼3 K in the helical magnetic phase, anomalous broadening of magnetic satellite reflections was observed in the directions perpendicular to the 1D magnetic chain, with a rapid change in the propagation wave number of helical magnetic ordering. Furthermore, in the antiferromagnetic phase below T 2 ∼1.9 K, CoNb 2 O 6 exhibits a pronounced 2D magnetic character. These features result from the competition between interchain exchange interaction and Co 2+ single-ion anisotropy in this compound.

Magnetic structure

10.1143/jpsj.63.3568

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Citations (20)