Jahn-Teller impurity dependence of the transition· . I 1 tetnper~ture Tcu· criticai exponent and pseudo~JahtiTeller p~tenthd -well splitting in ZoTiF6 • 6H20
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lOP· Publishing Ltd
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The 182.K (::.91.2 °C) trigohal-to-mouoclinic phase transition in ZnTiF6 • 6HP
_ sin&Je CI1(Stal has been studied by EPR, for various concentrations of doped Jahn-Teller (JT)
, .. - impar4ty Cu2+ ions and also for non-JT impurity NF+ ions. Tbe tr~nsition temperature Td
which decreases with increase in impurity concentration, is more strongly affected by the JT
impurity. The critical exponent {3 as well as the JT potential well splitting E0 have been
determiqd from the temperature variation in EPR signal intensity in the immedi-ate neighbourhood
ef Tc1 for the Cu2+ impurity. The critical exponent {3 and E0 are dependent
strongly on the JTimpurity concentmtioP For two different concentrations of Cu2+ ions, i.e. :
0.043 wt% and 0.98 wt%, the values of p ,,;e().5 ± 0.05 and 0.12 ± 0.03, respectively, while
the values of E0.are 140 ± 15 cm-J -and-97.:!; 1.1 cm-1, respectively. The valN.e of £ 0 for a
deuteratcd crystal containing a low Cu2+ conccntrati~s 78 ± 10 cm-1• The dec.rease in E0
with incn:asing Cu2
t c.oncentration fur a hydrated crystal and also with deuteration (for n
, low copper concentration) is in qualitative agreement with the corresponding gradual phase
. transition observed in these materials
Keywords
Q Science (General), QC Physics