Replace the line self.R = torch.tensor([[0.01]], requires_grad=True) with self.R = torch.nn.Parameter(torch.tensor([[0.01]])). After that modification, the parameters will be properly registered, so they will reside in the model’s state dict. And you should remove your own implementation of the method parameters as well.
Note that by default, a tensor that is wrapped in a torch.nn.Parameter has requires_grad=True.