
I can't find the LaTeX command and symbol and its package of this symbol. Can any one suggest me the command. I tried \mathcal{F} but its not exactly the same.
Use euscript's \EuScript:

\documentclass{article}
\usepackage{euscript}
\begin{document}
$\mathcal{F} \neq \EuScript{F}$
\end{document}