How to Write Japanese Names

[Antonio Ruiz]

I was wondering why is it that sometimes they leave a space between surname and given name when writing in Japanese characters and other times they don't leave any space at all. This is the case with Ayumi's name.
I've seen it written like this 浜崎あゆみ and also like this 浜崎 あゆみ

Which is the correct way? or can it be either way? Thanks for your help.