Magnetic Anomaly and Icosahedral Phase Formation in Fe-Cu and Fe-Mo Systems
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MAGNETIC ANOMALY AND ICOSAHEDRAL PHASE FORMATION IN Fe-Cu AND Fe-Mo SYSTEMS L.J. Huang, Q.M. Chen, B.X. Liu*, Y.D. Fan and H-D. Li Department of Materials Science and Engineering, Tsinghua University, Beijing, 100084, China *Also at Center of Condensed Matter and Radiation Physics, CCAST(World Lab), Beijing, China ABSTRACT The first observation of a new class of a magnetic transition in associated with It is found that the systems are reported. can be re-established when the destabilized
icosahedral phase Fe-Mo Fe-Cu and icosahedral order Fe 60Cu40 icosahe-
dral phase subject to a magnetic transition at high annealing The Fe 7 0 Mo 3 0 amorphous films obtained by sputtemperature. tering exhibit a similar behavior at high magnetic transition A brief discussion of the observed phenomena is temperature. addressed. INTRODUCTION It has been thought that icosahedral phase can only be formed in alloy systems which have proper off-stoichiometry of icosahedral local compounds or pre-formed the intermetallic results are largely order [1] and the reported experimental from aluminum-based alloy systems. It is therefore of interest to study the possibility of forming icosahedral phase in systems out of the above mentioned empirical rules. Some studies of the magnetic properties of Al-Mn and Al-Mn-Si icosahedral phase revealed that icosahedral structure has some special maof the To Further unravel the origin gnetic features [2-4]. purphase and for practical magnetic anomaly of icosahedral pose, it is also of interest to bring more experimental eviden In this paper, we report our experimental ces on this issue. formed associated of icosahedral phases which observations with a magnetic anomaly in Fe-Cu and Fe-Mo systems. EXPERIMENTAL The Fe 60Cu40 icosahedral phase was formed
by ion mixing
which were prepared in a va the Fe/Cu multilayered samples, using 300 keV inert Xenon cuum system, at room temperature + 2 16 ions upto an ion fluence of 1X1O Xe+/cm . The films were then transmission 200-CX subject to in situ thermal annealing in While the electron microscope (TEM) to study the stability. the Fe70Mo30 amorphous films were obtained by co-sputtering onto KCl single crystals by using a planar constituent metals Anneamagnetron sputtering apparatus with complex targets. out ling of the formed Fe-Mo amorpjous film was also carried in TEM. All the structural characterization was then by analysesing the diffraction patterns obtained by TEM. Magnetic susceptibility was measured by vibrating sample magnetometer(VSM
Mat. Res. Soc. Symp. Proc. Vol. 128. t1989 Materials Research Society
226
9500). The detailed experimentation can be found in vious publications [5,6].
our pre-
RESULTS AND DISCUSSIONS Fe-Cu system Thermal stability
study of the Fe 60Cu40 icosahedral phase
formed by ion mixing at room temperature[5] showed that this new metastable phase was easy to destablize when it was kept at an annealing temperature of 300 °C for more than one hour. When it happened, this new phase decomposed into a mixture of metastable bcc an
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