my problem is that I need more digits in the y ticks. When used precision=4, the y label and y ticks are superposed. ¿How can I avoid this?
\documentclass{article}
\usepackage{pgfplots}
\begin{document}
\pgfplotsset{xmin=275, xmax=525, ymin=0.3135, ymax=0.3145}
\begin{tikzpicture}[scale=0.75]
\begin{axis}[legend pos=south east,xlabel=$T\; \mathrm{(K)}$, ylabel=$f_{\mathrm{N_2}}$,xtick = {300,400,500},y tick label style={/pgf/number format/fixed,/pgf/number format/precision=4}]
\addplot[color=red,style=ultra thick]
coordinates{
(300,0.313962276936297)
(400,0.314247035933962)
(500,0.314270686043259)
};
\addplot[color=red, only marks,mark size=3.25pt]
coordinates{
(300,0.313962276936297)
(400,0.314247035933962)
(500,0.314270686043259)
};
\end{axis}
\end{tikzpicture}
\end{document}
\documentclass{...}
and loading all necessary packages.