Harassment post leaving job

It's been 3 months I have left the organisation, few of the colleagues who are still employed there , are spreading rumours about me in a very questionable way, It is regarding my work there, they are stating that she has left in a wrong way and so on , which is mentally threatening me to the core. Can I write a mail to the owner of the company as the HR does not seems cooperative. Or what actions can I take legally against those 3 employees. A quick advice required.