Tensorflow using float64 tensor

I have a feed-forward neural network with a customized cost function. Since my cost function has an exponential component, I need to handle very large numbers. By default, tensorflow uses float32 datatype, which is not sufficient for my work. How can I have a tensorflow model with float64 datatype? I have tried to define all the tensors as float64 and hope the casting take care of the rest but it does not work. Also, I have enabled the eager execution mode.