The thermal expansion and magnetostriction of the HoFe11
xCoxTi (0rxr11) alloys have been investigated, using the strain gauge technique in the temperature range 77–600 K. Both thermal expansion and thermal expansion coefficient exhibit an anomalous behaviour and Invar effect below Curie temperature (TC¼516 K) in sample with x¼0. The increase of x in HoFe11
xCoxTi system leads to disappearing of the Invar effect and increasing of the average thermal expansion coefficient from 6.37010
6 K
1 in x¼0 to 10.73510
6 K
1 in x¼11 below room temperature. In addition, the spontaneous volume magnetostriction decreases with Co content. The magnetostriction compensation point is observed in the anisotropic magnetostriction curve of all samples. The maximum value of anisotropic magnetostriction (ΔλE5010
6) at room temperature is observed in sample with x¼9. The saturation behaviour only appears in samples with x¼5, 7 and 9. In samples with x¼3, 5 and 7, a noticeable volume magnetostriction (ΔV/V) is observed in low temperature due to first-order magnetisation process. Moreover, ΔV/V exhibits a large anomaly about 4510
6 and 2010
6 around room temperature related to spin reorientation transition in samples with x¼9 and 11, respectively. The results are discussed based on the local magnetic moment model and irreducible magnetoelastic coupling modes.

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