All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu 'alyhi wa sallam, is His slave and Messenger.
It was narrated on the authority of ‘Abdullaah ibn Mas‘ood that the Prophet, sallallaahu ‘alayhi wa sallam, said that amulets and unlawful Ruqyah (healing with incantations) are considered Shirk (polytheism). [Imam Ahmad, Abu Daawood and Ibn Maajah] In Jaahiliyyah (the pre-Islamic era), people used to hang similar objects for protection. Therefore, anyone who thinks that such amulets may bring harm or benefit without the will of Allaah The Almighty is a polytheist committing a major act of Shirk that turns them into an apostate. However, if a person believes an amulet can be a means of protection against the evil eye and Jinn, they are committing a minor act of Shirk and a major sin.
The Ruqyah referred to in the Hadeeth refers to that which involves polytheism. However, there are different opinions from scholars regarding Ruqyah that includes the Quran and Names of Allaah. The dominant opinion is that it is not permissible to hang such things if the person does so while believing that it will bring benefit or remove harm.
On the other hand, hanging scent or ornaments is permissible, as such things are not an amulet or unlawful Ruqyah. Al-Baaji said that a necklace worn on the neck of a camel is alright if it is just an ornament. It was also reported that ‘Eesa ibn Deenaar held this same opinion. Therefore, hanging scent to perfume a place or a car or putting an ornament there is permissible.
Allaah Knows best.