Well that's not an easy question to answer. There are spray repellents you can use to protect certain areas of your yard, but they don't always work well in protecting an entire backyard. With rats you probably will need to use snap traps baited with peanut butter to eliminate these pests. Cats are a bit more difficult, but since free-roaming cats are generally not allowed in most urban areas, you probably should call animal control to remove them. There is no easy answer here. Spray repellents for cats are generally available at places like Lowe's, Home Depot, Wal-Mart, etc.