CRITICAL-BEHAVIOR OF ANTIPHASE BOUNDARIES IN FE3AL CLOSE TO THE DO3-]B2 PHASE-TRANSITION

By combining weak beam and conventional dark field transmission electr on microscopy observations, we have determined the critical behavior o f antiphase boundaries (APB) close to the second order DO3-B2 order-di sorder transition in Fe3Al. The weak beam technique is particularly ac curate since the intensity of the APE fringes decreases exponentially when the width of the boundaries, proportional to the correlation leng th xi, increases. The measured critical exponent v = 0.64 +/- 0.1 is i n good agreement with theory as well as with scattering experiments in the B2 phase.