For temporary deactivation, just turn off real-time protection, cloud-delivered protection and sample submission in the settings (Virus and Threat Protection) ... if you want to stop it permanently, add a new DWORD "DisableAntiSpyware" to "HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender" in registry or enable the Local Group Policy ... there's a template called something like "Turn off Windows Defender".