Time series beginner help urgent!!

Hi, just looking for some help from anyone familiar with ARIMA modelling of time series. I am trying to get a stationary series from my data, I differenced the data and the following plots are of the time series and PACF of the differenced data:


The ACf plot cuts off after lag one, can anyone suggest whether these graphs display values consitent with an IMA(1,1) model? That is my hypothesis but I would like the opinion of someone who is familiar with this stuff.

Thanks for any help