Magnetic properties of vanadium oxide nanotubes and nanolayers

被引：18

作者：

Demishev, S. V. ^{[1
]}

Chernobrovkin, A. L. ^{[1
,2
]}

Glushkov, V. V. ^{[1
]}

Grigorieva, A. V. ^{[3
]}

Goodilin, E. A. ^{[3
]}

Ohta, H. ^{[4
]}

Okubo, S. ^{[4
]}

Fujisawa, M. ^{[4
]}

Sakurai, T. ^{[5
]}

Sluchanko, N. E. ^{[1
]}

Samarin, N. A. ^{[1
]}

Semeno, A. V. ^{[1
]}

机构：

[1] AM Prokhorov Gen Phys Inst RAS, Moscow 119991, Russia

[2] Russian Acad Med Sci, Inst Biomed Chem, Moscow 119121, Russia

[3] Moscow MV Lomonosov State Univ, Dept Mat Sci, Moscow 119991, Russia

[4] Kobe Univ, Mol Photosci Res Ctr, Nada Ku, Kobe, Hyogo 6578501, Japan

[5] Kobe Univ, Ctr Supports Res & Educ Act, Kobe, Hyogo 6758501, Japan

来源：

PHYSICAL REVIEW B | 2011年 / 84卷 / 09期

基金：

日本学术振兴会;

关键词：

QUANTUM CRITICAL PHENOMENA; ELECTRON-SPIN-RESONANCE; ANTIFERROMAGNETIC SYSTEM; CRITICAL-BEHAVIOR; SUSCEPTIBILITY;

D O I：

10.1103/PhysRevB.84.094426

中图分类号：

T [工业技术];

学科分类号：

08 ;

摘要：

We report results of magnetic measurements of VO(x) nanolayers (stacks of four to eight distorted layers of vanadium oxide separated by an organic template) obtained at the early stages of a hydrothermal synthesis of VO(x) nanotubes (VO(x) NTs), and VO(x) NTs themselves, which are the product of scrolling of VO(x) nanolayers (VO(x) NLs). Static and dynamic magnetic properties of VO(x) NLs and VO(x) NTs have been studied by means of a high-frequency (60 GHz) ESR and SQUID magnetometry in a temperature range 1.8-300 K. The temperature dependence of the magnetic susceptibility chi of the V(4+) quasifree spins in VO(x) NTs and VO(x) NLs shows a transition from the Curie-Weiss laws with close paramagnetic temperatures Theta(AFM) = -25 K (VO(x) NTs) and Theta(AFM) = -19 K (VO(x) NLs) to the low-temperature power law chi alpha 1/T(xi) with xi = 0.75 (VO(x) NTs) and xi = 0.85 (VO(x) NTs). The observed.(T) dependence for quasifree spins was adequately described within an analytical model of an antiferromagnetic system with a disorder-driven quantum critical behavior. Comparison of static and dynamic susceptibilities reveals that the total magnetic susceptibility in VO(x) NLs and VO(x)-NTs consists of several contributions. Apart from the oscillating susceptibility, there is a nonoscillating background, likely, consisting of the Van Vleck-type and Pauli-type terms. In the case of VO(x) NTs, a correlated change of the Curie constant for the nondimerized V(4+) quasifree spins and a variation of the background are observed: the decrease in temperature in the interval 70 K < T < 120 K induces 1.8-fold growth of the Curie constant followed by a nonoscillating background decrease along with a change of its sign. The estimated concentration of magnetic sites indicates that a characteristic feature of VO(x) NLs and VO(x) NTs is a discrepancy between the maximal possible concentration of V(4+) magnetic ions that is allowed by a chemical composition, and a concentration of the localized magnetic moments. The number of electrons in the V(4+) state is always less than the total electron concentration, and the concentration of the "excessive" electrons may vary in the range 0.11-0.46 per vanadium site. At the same time, the concentration of V(4+)-V(4+) antiferromagnetic dimers in VO(x) NTs is rather high and reaches 49% of all vanadium sites. The effects of scrolling and Mott-Hubbard-type models of unusual magnetism in the VO(x) nanomaterials are discussed.

引用

页数：11

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