The 22-year-old was released by the Terriers prior to last week's transfer deadline, having made just two first-team appearances for the Yorkshire club.
Spencer will wear the number 16 shirt during his spell at Meadow Lane.
He is likely to make his debut for the Magpies in Saturday's League One clash with Coventry City.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| C | Stockport CountyStockport | 46 | 27 | 11 | 8 | 96 | 48 | 48 | 92 |
| P | Wrexham | 46 | 26 | 10 | 10 | 89 | 52 | 37 | 88 |
| P | Mansfield TownMansfield | 46 | 24 | 14 | 8 | 90 | 47 | 43 | 86 |
| 4 | MK Dons | 46 | 23 | 9 | 14 | 83 | 68 | 15 | 78 |
| 5 | Doncaster RoversDoncaster | 46 | 21 | 8 | 17 | 73 | 68 | 5 | 71 |
| 6 | Crewe AlexandraCrewe | 46 | 19 | 14 | 13 | 69 | 65 | 4 | 71 |
| 7 | Crawley TownCrawley | 46 | 21 | 7 | 18 | 73 | 67 | 6 | 70 |
| 8 | BarrowBarrow | 46 | 18 | 15 | 13 | 62 | 56 | 6 | 69 |
| 9 | Bradford CityBradford | 46 | 19 | 12 | 15 | 61 | 59 | 2 | 69 |
| 10 | AFC Wimbledon | 46 | 17 | 14 | 15 | 64 | 51 | 13 | 65 |
| 11 | Walsall | 46 | 18 | 11 | 17 | 69 | 73 | -4 | 65 |
| 12 | Gillingham | 46 | 18 | 10 | 18 | 46 | 57 | -11 | 64 |
| 13 | Harrogate TownHarrogate | 46 | 17 | 12 | 17 | 60 | 69 | -9 | 63 |
| 14 | Notts County | 46 | 18 | 7 | 21 | 89 | 86 | 3 | 61 |
| 15 | Morecambe | 46 | 17 | 10 | 19 | 67 | 81 | -14 | 58 |
| 16 | Tranmere RoversTranmere | 46 | 17 | 6 | 23 | 67 | 70 | -3 | 57 |
| 17 | Accrington StanleyAccrington | 46 | 16 | 9 | 21 | 63 | 71 | -8 | 57 |
| 18 | Newport CountyNewport | 46 | 16 | 7 | 23 | 62 | 76 | -14 | 55 |
| 19 | Swindon TownSwindon | 46 | 14 | 12 | 20 | 77 | 83 | -6 | 54 |
| 20 | Salford City | 46 | 13 | 12 | 21 | 66 | 82 | -16 | 51 |
| 21 | Grimsby Town | 46 | 11 | 16 | 19 | 57 | 74 | -17 | 49 |
| 22 | Colchester UnitedColchester | 46 | 11 | 12 | 23 | 59 | 80 | -21 | 45 |
| R | Sutton UnitedSutton | 46 | 9 | 15 | 22 | 59 | 84 | -25 | 42 |
| R | Forest Green RoversForest Green | 46 | 11 | 9 | 26 | 44 | 78 | -34 | 42 |
| > League Two Full Table | |||||||||
