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КОНДЕНСИРОВАННЫЕ СРЕДЫ
Electron Transport in Diborides: Observation of Superconductivity in ZrB$_2$
V. A. Gasparov,
N. S. Sidorov,
I. I. Zver'kova,
M. P. Kulakov Institute of Solid State Physics, Russian Academy of Sciences
Аннотация:
We report on syntheses and electron transport properties of polycrystalline samples of diborides (AB
$_2$) with different transition metals atoms (A
${}={}$Zr,Nb,Ta). The temperature dependence of resistivity,
$\rho(T)$, and
ac susceptibility of these samples reveal superconducting transition of ZrB
$_2$ with
$T_c=5.5\,$K, while NbB
$_2$ and TaB
$_2$ have been observed nonsuperconducting up to
$0.37$ K.
$H_{c2}(T)$ is linear in temperature below
$T_c$, leading to a rather low
$H_{c2}(0)= 0.1\,$T. At
$T$ close to
$T_c$ $H_{c2}$ $(T)$ demonstrates a downward curvature. We conclude that these diborides as well as MgB
$_2$ samples behaves like a simple metals in the normal state with usual Bloch–Grüneisen temperature dependence of resistivity and with Debye temperatures:
$280$,
$460$ and
$440$ K, for ZrB
$_2$, NbB
$_2$ and MgB
$_2$, respectively, rather than
$T^2$ and
$T^3$ as previously reported for MgB
$_2$.
PACS:
72.15.Gd,
74.70.Ad, 74.60.Ec,
Поступила в редакцию: 12.04.2001
Язык публикации: английский