PECULARIR MAGNETIC BEHAVIOR AND SUPERCONDUCTIVITY IN AMORPHOUS (AND SULFUR DOPED) CARBON MATERIALS

actorrattleUrban and Civil

Nov 15, 2013 (3 years and 6 months ago)

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PECULARIR MAGNETIC B
EHAVIOR AND
SUPERCONDUCTIVITY IN

AMORPHOUS

(AND SULFUR DOPED) C
ARBON MATERIALS


I.

Felner


1
Racah Institute of Physics, The Hebrew University, Jerusalem, Israel


I shall shortly review previous published experimental results that provid
e evidences
for intrinsic supercoductivity (SC) and magnetic features in carbon based materials.
The SC of graphite
-
sulfur composites (T
C
=35 K) is anisotropic and associated with
the graphite planes. SC occurs in a small fraction of the materials.

We studi
ed
amorphous carbon

(aC) samples which
are
75 years old !!!
.

It appears
that one of the samples studied, is superconducting (T
C
=39 K) but the SC fraction is
very tiny. An heated mixture at 523 K of aC with sulfur increases significanly the SC
fraction.

T
he magnetic properties of (i) aC and (ii) sulfur doped in aC materials have shown
that aC

is magnetically highly inhomogeneous. In all samples we observed a large
zero
-
field
-
cooled (
M
ZFC
) and field
-
cooled (
M
FC
) thermal hysteresis in the
magnetization curve
s up to room temperature. A paramagnetic
-
like behavior at low
temperatures and a pronounced peak at 65
-
80 K were observed in
M
ZFC

branches.
These peaks may imply spin orientation of carbon atoms with localized electrons.
A
similar behavior is obtained in t
he sulfur doped samples. However, a comlex inter
-
relation between the
M
ZFC

and
M
FC

branches is obsaerved. In some cases the
M
FC

curves cross the
M
ZFC

peaks, and unexpectedly and in one case the
M
ZFC

curve lies
above

the
M
FC

in the entire temperature range
up 150 K. The magnetic features
observed are unstable and change within a few days.The origin of the peculiar
phenomena is not yet known
.