Heat capacity study of the doping effect of paramagnetic radicals on the organic spin-Peierls system (p-CyDOV radical crystal)

Kazuo Mukai, Masanobu Yanagimoyo, Shuichi Tanaka, Masaki Mito, Tatsuya Kawae, Kazuyoshi Takeda

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Abstract

The doping effect of paramagnetic organic radical impurities (p-CyDTV) on the organic spin-Peiels (SP) system of p-CyDOV (3-(4-cyanophenyl)-1,5-dimethyl- 6-oxoverdazyl; the SP transition temperature TSP = 15.0 K) was studied by the heat capacity measurement down to 0.1 K. At low temperatures below 1 K, quite a sharp heat capacity peak was detected for each system with small impurity concentration (x) at the temperature TN(x); T N(0) = 0.135 K (±0.002 K), TN(0.01) = 0.290 K and TN(0.07) = 0.164 K. The appearance of the peak for the system with x = 0 is considered to be due to minute and inevitable impurities in the pure p-CyDOV. From the dependence of TN(x), TN(0) < T N(0.01), and the heat capacity behavior on x, the peaks for x = 0 and 0.01 are explained to be accompanied with the three-dimensional (3D) antiferromagnetic (AFM) transition in the SP phase. While the decrease of T N(x) for higher impurities x = 0.07 than that for x = 0.01 may be interpreted as merely a 3D AFM transition from the paramagnetic state in the quasi-1D systems with the interchain interaction |zJ′/J| = 6 × 10-4. Although no anomaly of the heat capacity was found around TSP(x) = 13-15 K in the present systems, where the characteristic decrease of the magnetic susceptibility is reported, we observed a distinct hump of the heat capacity at T′SP(0) = 5.6 K and T′SP(0.01) = 5.3 K with magnetic entropy consumption up to 3%, suggesting that this transition may relate to SP transition.

Original languageEnglish
Pages (from-to)2312-2316
Number of pages5
Journaljournal of the physical society of japan
Volume72
Issue number9
DOIs
Publication statusPublished - Sep 1 2003

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specific heat
impurities
crystals
spin temperature
transition temperature
entropy
anomalies
magnetic permeability
interactions
temperature

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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Heat capacity study of the doping effect of paramagnetic radicals on the organic spin-Peierls system (p-CyDOV radical crystal). / Mukai, Kazuo; Yanagimoyo, Masanobu; Tanaka, Shuichi; Mito, Masaki; Kawae, Tatsuya; Takeda, Kazuyoshi.

In: journal of the physical society of japan, Vol. 72, No. 9, 01.09.2003, p. 2312-2316.

Research output: Contribution to journalArticle

Mukai, Kazuo ; Yanagimoyo, Masanobu ; Tanaka, Shuichi ; Mito, Masaki ; Kawae, Tatsuya ; Takeda, Kazuyoshi. / Heat capacity study of the doping effect of paramagnetic radicals on the organic spin-Peierls system (p-CyDOV radical crystal). In: journal of the physical society of japan. 2003 ; Vol. 72, No. 9. pp. 2312-2316.
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AB - The doping effect of paramagnetic organic radical impurities (p-CyDTV) on the organic spin-Peiels (SP) system of p-CyDOV (3-(4-cyanophenyl)-1,5-dimethyl- 6-oxoverdazyl; the SP transition temperature TSP = 15.0 K) was studied by the heat capacity measurement down to 0.1 K. At low temperatures below 1 K, quite a sharp heat capacity peak was detected for each system with small impurity concentration (x) at the temperature TN(x); T N(0) = 0.135 K (±0.002 K), TN(0.01) = 0.290 K and TN(0.07) = 0.164 K. The appearance of the peak for the system with x = 0 is considered to be due to minute and inevitable impurities in the pure p-CyDOV. From the dependence of TN(x), TN(0) < T N(0.01), and the heat capacity behavior on x, the peaks for x = 0 and 0.01 are explained to be accompanied with the three-dimensional (3D) antiferromagnetic (AFM) transition in the SP phase. While the decrease of T N(x) for higher impurities x = 0.07 than that for x = 0.01 may be interpreted as merely a 3D AFM transition from the paramagnetic state in the quasi-1D systems with the interchain interaction |zJ′/J| = 6 × 10-4. Although no anomaly of the heat capacity was found around TSP(x) = 13-15 K in the present systems, where the characteristic decrease of the magnetic susceptibility is reported, we observed a distinct hump of the heat capacity at T′SP(0) = 5.6 K and T′SP(0.01) = 5.3 K with magnetic entropy consumption up to 3%, suggesting that this transition may relate to SP transition.

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