\documentclass{report}
\usepackage{pslatex,palatino,avant,ifthen}
\usepackage[latin1]{inputenc}
\usepackage[T1]{fontenc}
\makeatletter
\renewcommand{\LaTeX}{L\ifthenelse{\equal{\f@family}{\sfdefault}}%
                                  {\ifthenelse{\equal{\f@series}{\bfdefault}}%
                                              {\kern-.24em}%
                                              {\kern-.3em}}%
                                  {\kern-.36em}%
        {\sbox\z@ T%
         \vbox to\ht\z@{\hbox{\check@mathfonts
                              \fontsize\sf@size\z@
                              \math@fontsfalse\selectfont
                              A}%
                        \vss}%
        }%
        \kern-.15em%
        \TeX}
\makeatother
\begin{document}\Huge\bfseries
This is \LaTeX\ and \sffamily this is \LaTeX\ in \sfdefault
\end{document}
