Magnetic properties and phase transitions in (CH3NH 2)K3C60 fulleride: An 1H and 2H NMR spectroscopic study

Denis Arčon; Alexey Y. Ganin; Yasuhiro Takabayashi; Matthew J. Rosseinsky; Kosmas Prassides

doi:10.1021/cm800578e

Magnetic properties and phase transitions in (CH₃NH ₂)K₃C₆₀ fulleride: An ¹H and ²H NMR spectroscopic study

Denis Arčon, Alexey Y. Ganin, Yasuhiro Takabayashi, Matthew J. Rosseinsky, Kosmas Prassides

Advanced Institute for Materials Research (AIMR)

Research output: Contribution to journal › Article › peer-review

8 Citations (Scopus)

Abstract

The hyperexpanded (CH₃NH₂)K₃C₆₀ fulleride and its perdeuterated analogue were investigated by ¹H and ²H NMR spectroscopy between room temperature and 4 K. Two phase transitions at T_S = 220 K and T_N = 11 K clearly were detected in the temperature dependence of the NMR line shapes, the spectral first (M₁ and second (M₂) moments, and the spin lattice relaxation times, T₁. From ²H NMR line shape analysis, we found that the structural phase transition at T_S was driven by the freezing out of the discrete Markovian-type jump motion of the entire K ⁺-ND₂CD₃ unit that is characterized by an activation energy, E_a = 236(51) meV. Below T_S, a sudden change in the temperature dependence of M₁ suggests the appearance of a small but nonzero spin density on the K⁺-NH₂CH ₃ unit. This could influence the electronic properties of the fulleride phase by modulating the strength of the exchange interactions between C₆₀^3- anions and controlling the width, W, of the t _1u-derived band. The ¹H NMR spectra below T_N show significant line broadening consistent with the onset of long-range antiferromagnetic order. ¹H NMR line shape calculations revealed the adoption of a type II magnetic structure with an ordering vector, q→_II = (1/2, 1/2, 1/2) and individual C₆₀ ^3- magnetic moments of magnitude (∼0.7 μ_B) aligned along the crystallographic a-axis.

Original language	English
Pages (from-to)	4391-4397
Number of pages	7
Journal	Chemistry of Materials
Volume	20
Issue number	13
DOIs	https://doi.org/10.1021/cm800578e
Publication status	Published - 2008 Jul 8

ASJC Scopus subject areas

Chemistry(all)
Chemical Engineering(all)
Materials Chemistry

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title = "Magnetic properties and phase transitions in (CH3NH 2)K3C60 fulleride: An 1H and 2H NMR spectroscopic study",

abstract = "The hyperexpanded (CH3NH2)K3C60 fulleride and its perdeuterated analogue were investigated by 1H and 2H NMR spectroscopy between room temperature and 4 K. Two phase transitions at TS = 220 K and TN = 11 K clearly were detected in the temperature dependence of the NMR line shapes, the spectral first (M1 and second (M2) moments, and the spin lattice relaxation times, T1. From 2H NMR line shape analysis, we found that the structural phase transition at TS was driven by the freezing out of the discrete Markovian-type jump motion of the entire K +-ND2CD3 unit that is characterized by an activation energy, Ea = 236(51) meV. Below TS, a sudden change in the temperature dependence of M1 suggests the appearance of a small but nonzero spin density on the K+-NH2CH 3 unit. This could influence the electronic properties of the fulleride phase by modulating the strength of the exchange interactions between C603- anions and controlling the width, W, of the t 1u-derived band. The 1H NMR spectra below TN show significant line broadening consistent with the onset of long-range antiferromagnetic order. 1H NMR line shape calculations revealed the adoption of a type II magnetic structure with an ordering vector, q→II = (1/2, 1/2, 1/2) and individual C60 3- magnetic moments of magnitude (∼0.7 μB) aligned along the crystallographic a-axis.",

author = "Denis Ar{\v c}on and Ganin, {Alexey Y.} and Yasuhiro Takabayashi and Rosseinsky, {Matthew J.} and Kosmas Prassides",

year = "2008",

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T2 - An 1H and 2H NMR spectroscopic study

AU - Arčon, Denis

AU - Ganin, Alexey Y.

AU - Takabayashi, Yasuhiro

AU - Rosseinsky, Matthew J.

AU - Prassides, Kosmas

PY - 2008/7/8

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N2 - The hyperexpanded (CH3NH2)K3C60 fulleride and its perdeuterated analogue were investigated by 1H and 2H NMR spectroscopy between room temperature and 4 K. Two phase transitions at TS = 220 K and TN = 11 K clearly were detected in the temperature dependence of the NMR line shapes, the spectral first (M1 and second (M2) moments, and the spin lattice relaxation times, T1. From 2H NMR line shape analysis, we found that the structural phase transition at TS was driven by the freezing out of the discrete Markovian-type jump motion of the entire K +-ND2CD3 unit that is characterized by an activation energy, Ea = 236(51) meV. Below TS, a sudden change in the temperature dependence of M1 suggests the appearance of a small but nonzero spin density on the K+-NH2CH 3 unit. This could influence the electronic properties of the fulleride phase by modulating the strength of the exchange interactions between C603- anions and controlling the width, W, of the t 1u-derived band. The 1H NMR spectra below TN show significant line broadening consistent with the onset of long-range antiferromagnetic order. 1H NMR line shape calculations revealed the adoption of a type II magnetic structure with an ordering vector, q→II = (1/2, 1/2, 1/2) and individual C60 3- magnetic moments of magnitude (∼0.7 μB) aligned along the crystallographic a-axis.

AB - The hyperexpanded (CH3NH2)K3C60 fulleride and its perdeuterated analogue were investigated by 1H and 2H NMR spectroscopy between room temperature and 4 K. Two phase transitions at TS = 220 K and TN = 11 K clearly were detected in the temperature dependence of the NMR line shapes, the spectral first (M1 and second (M2) moments, and the spin lattice relaxation times, T1. From 2H NMR line shape analysis, we found that the structural phase transition at TS was driven by the freezing out of the discrete Markovian-type jump motion of the entire K +-ND2CD3 unit that is characterized by an activation energy, Ea = 236(51) meV. Below TS, a sudden change in the temperature dependence of M1 suggests the appearance of a small but nonzero spin density on the K+-NH2CH 3 unit. This could influence the electronic properties of the fulleride phase by modulating the strength of the exchange interactions between C603- anions and controlling the width, W, of the t 1u-derived band. The 1H NMR spectra below TN show significant line broadening consistent with the onset of long-range antiferromagnetic order. 1H NMR line shape calculations revealed the adoption of a type II magnetic structure with an ordering vector, q→II = (1/2, 1/2, 1/2) and individual C60 3- magnetic moments of magnitude (∼0.7 μB) aligned along the crystallographic a-axis.

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