To translate the phrase literary, it should be like “日誌の投稿 (にっしのとうこう / Nisshi no Toukou)”. 日誌 sounds more matured than 日記 (にっき / Nikki / diary) as it does in English; however, people here prefer call it just as エントリー (entry), ポスト (post), or 投稿 (post). It also works the same as in English. I suppose you say “a next entry” in general, not “a next journal entry” except when you want to emphasize that the entry is a journal. And if you refer to something like a blog post, 記事 (きじ / Kiji) works fine. It means an article, but only online the word is used extensively including even when the post is actually a mere personal diary.