Magneto-structural coupling induced multiple magnetic transitions and magnetocaloric effect of Ni43Mn46Sn9Ge2 alloy

•Magnetic property of Heusler alloy Ni43Mn46Sn9Ge2 with excess Mn was studied in detail.•The visible exchange bias, large coercivity and double-shifted hysteresis behaviors at low temperatures were observed and discussed.•Multiple magnetic phase transitions induced by magneto-structural coupling result in direct and inverse magnetocaloric effects.•Under µ0H = 5 T, the maximum value of magnetic entropy change (ΔSMmax) reaches 22.88 J/kg.K, the refrigeration capacity (RC) reaches 125.89 J/kg.•ΔSMmax increases at a rate of 4.58 J/kg.K per Tesla, while RC increases at a rate of 25.18 J/kg per Tesla.