Finding the SObjectType from the SObjectField

I don't believe this is possible currently. There's no methods on Schema.SObjectField of Schema.DescribeFieldResult that link back to the SObjectType that field belongs to.

I know this is a little old, but I was searching how to solve this problem and I couldn't find anything useful. This is how I solved it:

Type myObjectType = MyObject__c.myField__c.class;
String myObjectName = myObjectType.toString(); // You can use getName() as well

That code will give you the Type of MyObject__c class. Then you can use all the methods for Type class in Apex like toString() or getName() to get the String name of MyObject__c.

Please check Salesforce Type Class for more info.