Consider the following Landau Free Energy (G) expression, as a function of order parameter(Q), conjugate external field

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Consider The Following Landau Free Energy G Expression As A Function Of Order Parameter Q Conjugate External Field 1 (63.69 KiB) Viewed 12 times

Consider the following Landau Free Energy (G) expression, as a function of order parameter(Q), conjugate external field (H) and temperature (T): G=(T – T.)Q2 + q* + 26 – H.Q equation 12.1 where Te is the Curie Temperature and a, b and c are scalar constants. (i) Explain the origin of the (T-T.) prefactor. [5] (ii) In the absence of an applied field (i.e. H = 0), sketch graphically the manner in which the Landau Free Energy, implied by equation 12.1, develops on cooling through Te for two different cases: firstly, when b > 0 and c = 0 and secondly, when b< 0 and c > 0. [5] (iii) With two further sketches, show how the Landau Free Energy functions for these two cases are altered whenever a finite external field is applied (i.e. H = 0). [4] (iv) Using equation 12.1 as a starting point, develop an expression for the susceptibility of the order parameter to the applied field and hence discuss the phenomenon of transformation plasticity. [6]