Low Temperature Martensitic Transition in a Pu-Ga AlloyTai C. Chiang

Department of Physics. University of Illinois at Uranba-Champaign

X-ray thermal diffuse scattering mapping (TDS) of phonons in Pu-Ga: Results show that the L-point soft mode in Pu-Ga does not change as the temperature is lowered toward the transition temperature. This is rather unusual and points to the collective response or instability of the 5f electronic configuration as a likely driving mechanism for the transition.

TDS patterns from a (111) grain and a (110) grain at different temperatures and the corresponding fits.

Temperaure T (arb units)

Phon

on F

requ

ency

(arb

uni

ts)

(a) First Order, Type A

(b) First Order, Type B

(c) Second Order

TCT0

TC

TC Example: TiSe2

Pu

-La-Ce

Temperaure T (arb units)

Phon

on F

requ

ency

(arb

uni

ts)

(a) First Order, Type A

(b) First Order, Type B

(c) Second Order

TCT0

TC

TC Example: TiSe2

Pu

-La-Ce

Phonon frequency as a function of temperature for different types of transitions.