4 FIG. 6: (Color online) Field vs temperature phase di- agram determined by the temperature of the maximum ∂M/∂T < 0 slope and the C m ( T C ) jump and the cusp of M ( T M ). Inset: detailed of the critical region using the criterion of the maximum slope of ∂M/∂B | max , showing the site ’U’ of the observed structure (see the text). Error bar for the U-region boundary determination is ± 7 mT FIG. 5: (Color online) (a) Isothermal field derivative of the magnetization between 2 and 5 K and (b) detail between 3 . 8 ≤ T ≤ 5 K showing an incipient structure in the max- imum of the derivative around the critical point. Dashed curves mark the maximum slope of those derivatives ∂M/∂B |$_{T}$ as a function of field may correspond to one of the steps predicted in the M ( B ) dependence, which in this case corresponds to ≈ 1 / 8 of the satu- rated moment M$_{S}$ . The weakness of this effect can be attributed to the poly-crystalline character of the samples. As proposed in Ref.[8] for B = 0, Ce nearest- neighbors form FM pairs with effective spin S$_{eff}$ = 1 which define a simple square lattice lying parallel to the basal plane. A ShSu phase builds up from those dimers at T = T$_{M}$ , which interact antiferromagneti- cally among them. From the present results we ob- serve that dimers keep forming under moderate exter- nal field. However, the fact that the C$_{m}$ ( T$_{C}$ ) jump and the height of the ∂M/∂B |$_{T}$ maxima decrease as T$_{C}$ ( B ) → T$_{M}$ indicates that the degrees of freedom in- volved in the formation of the intermediate phase are progressively reduced by increasing magnetic field. IV. CONCLUSIONS The field dependent magnetic phase diagram was established for Ce 2 Pd 2 Sn. The application of mag- netic field confirms that the transition at T = T$_{M}$ can- not be regarded as a canonical AF transition since T$_{M}$ is practically not affected by fields of moderate inten- sity. On the contrary, the low temperature FM phase is favored by field since the AF interaction among dimers in the intermediate phase is progressively sup- pressed. The instability of the intermediate Shasry- Sutherland phase in this compound is confirmed by the low value of applied field B$_{cr}$ ≈ 0 . 12 T required for its suppression. Around the critical region, a weak B = 0 . 15 T at T = 4 . 2 K, see dashed curves in Fig.5b. Above that temperature the satellite maximum pro- gressively vanishes, disappearing at T ≈ 4 . 7 K. Such a split of the ∂M/∂B |$_{T}$ derivative might be due to the formation of a field induced phase when the point is approached. This feature my be related to one of the predictions for the ShSu lattice, that is the appear- ance of a plateaux in the magnetization at 1/4, 1/8 and 1/10 of the full saturated moment, as different or- dered states emerge from the initially frustrated spin liquid through the application of magnetic field [4]. The obtained magnetic phase diagram is presented in Fig.6. There, the field driven transition between intermediate and FM phases is drawn according to the temperature of the maximum slope ∂M/∂T |$_{max}$ , which is in agreement with C$_{m}$ ( T ) measurements. Since T$_{M}$ is practically not affected by field, both phase boundaries join at a critical point, at T$_{cr}$ = (4 . 2 ± 0 . 3)K for B$_{cr}$ = (0 . 12 ± 0 . 02)T. In the inset of Fig. 6 we show a detail of the critical region extracted from the maximum slopes of the M/∂B |$_{T}$ ( B ) derivatives depicted in Fig.5b. As mentioned before, the structure observed in the