The cdf of single magnitute is (see < $$ F(x)=(1-e^{-x}) $$ and the maximum magnitude is (see < $$F(x)=(1-e^{-x})^n$$ and thus the pdf (just by differentiating) is $$f(x)=n(1-e^{-x})^{n-1}e^{-x}\textrm{.}$$
The cdf of single magnitute is (see < $$ F(x)=(1-e^{-x}) $$ and the maximum magnitude is (see < $$F(x)=(1-e^{-x})^n$$ and thus the pdf (just by differentiating) is $$f(x)=n(1-e^{-x})^{n-1}e^{-x}\textrm{.}$$